| Name | Nation | Sport | Games | Notes |
|---|
| O Tae-geun | South Korea | Wrestling | 1952 Summer, 1956 Summer | |
| Asako O | Japan | Basketball | 2016 Summer | |
| O Chang-ran | North Korea | Football | 2012 Summer | |
| O Cheong-ja | South Korea | Volleyball | 1964 Summer | |
| O Go-un | Field hockey | 2000 Summer, 2004 Summer | |
| O Gwang-sun | North Korea | Archery | 1980 Summer | |
| O Hui-sun | Football | 2012 Summer | |
| O Il | Table tennis | 2004 Summer | |
| O Jong-ae | Weightlifting | 2008 Summer | |
| O Jong-yeol | South Korea | Sailing | 1988 Summer | |
| O Pyeong-gil | Volleyball | 1964 Summer | |
| O Song-chol | North Korea | Boxing | 1992 Summer | |
| O Song-nam | Wrestling | 2004 Summer | |
| O Su-cheol | South Korea | Basketball | 1948 Summer | |
| O Sun-ok | Volleyball | 1964 Summer | |
| O Uk-hwan | 1992 Summer | |
| Mircea Oaidă | Romania | Athletics | 1992 Summer | |
| John Oakeley | Great Britain | Sailing | 1972 Summer | |
| Gary Oakes | Athletics | 1980 Summer | |
| Heather Oakes | 1980 Summer, 1984 Summer | |
| John Waddington Oakes | Alpine skiing | 1960 Winter | |
| Judy Oakes | Athletics | 1984 Summer, 1988 Summer, 1996 Summer, 2000 Summer | |
| Alex Oakley | Canada | 1956 Summer, 1960 Summer, 1964 Summer, 1972 Summer, 1976 Summer | |
| Débora Oakley | Mexico | Rowing | 2012 Summer | |
| Delceita Oakley | Panama | Athletics | 1964 Summer | |
| Alexandru Oancea | Romania | Bobsleigh | 1964 Winter | |
| Ecaterina Oancia | Rowing | 1984 Summer, 1988 Summer | |
| Ilie Oanță | 1972 Summer | |
| Iolanda Oanță | Athletics | 1992 Summer | |
| Nicolae Oanță [ Wikidata ] | Water polo | 2024 Summer | |
| Colin Oates | Great Britain | Judo | 2012 Summer, 2016 Summer | |
| Shelley Oates-Wilding | Australia | Canoe sprint | 1996 Summer, 2000 Summer | |
| Kristy Oatley | Equestrian dressage | 2000 Summer, 2008 Summer, 2012 Summer, 2016 Summer | |
| Lyndal Oatley | 2012 Summer, 2016 Summer | |
| Derek Oatway | Bermuda | Swimming | 1948 Summer | |
| Nicole Oba | Republic of the Congo | Handball | 1980 Summer | |
| Slavko Obadov | Yugoslavia | Judo | 1972 Summer, 1976 Summer, 1980 Summer | |
| Abiodun Obafemi | Nigeria | Football | 1996 Summer | |
| Darren Obah | Australia | Boxing | 1988 Summer | |
| Musa Amer Obaid | Qatar | Athletics | 2004 Summer | |
| Aker Al-Obaidi | Refugee Olympic Team | Wrestling | 2020 Summer | |
| Abdul Aziz Al-Obaidly | Qatar | Swimming | 2020 Summer, 2024 Summer | |
| Abdulnasser Al-Obaidly | Football | 1992 Summer | |
| Anthony Obame | Gabon | Taekwondo | 2012 Summer, 2016 Summer, 2020 Summer | |
| Marvin Obando | Costa Rica | Football | 1980 Summer, 1984 Summer | |
| Omar Obando [ Wikidata ] | Nicaragua | Baseball | 1996 Summer | |
| Hitomi Obara | Japan | Wrestling | 2012 Summer | |
| Tadashi Obara | Speed skating | 2010 Winter | |
| Takumi Obara | Triathlon | 2000 Summer | |
| Yuri Obara | Speed skating | 2002 Winter | |
| Yuta Obara | Track cycling | 2024 Summer | |
| Alberto Obarrio | Argentina | Sailing | 1968 Summer | |
| Chinedu Obasi | Nigeria | Football | 2008 Summer | |
| Derrick Obasohan | Basketball | 2012 Summer | |
| Michael Obasuyi | Belgium | Athletics | 2020 Summer, 2024 Summer | |
| Atsushi Obata | Japan | Rowing | 2000 Summer | |
| Hiroyuki Obata | Wrestling | 1988 Summer | |
| Kunihiko Obata | 2004 Summer | |
| Ryuichi Obata | Equestrian jumping | 1976 Summer, 1984 Summer, 2004 Summer | |
| Saori Obata | Tennis | 2004 Summer | |
| Satsuki Obata | Artistic gymnastics | 1996 Summer | |
| Atsushi Obayashi | Swimming | 1964 Summer | |
| Motoko Obayashi | Volleyball | 1988 Summer, 1992 Summer, 1996 Summer | |
| Yumi Obe | Football | 1996 Summer | |
| Irina Obedina | Russia | Athletics | 2008 Summer | |
| Patricia Obee | Canada | Rowing | 2012 Summer, 2016 Summer | |
| Guillermo Obeid | Argentina | Fencing | 1968 Summer | |
| Kheir El-Din Obeid | Syria | Athletics | 1992 Summer | |
| Kirsten Obel | Germany | Shooting | 1996 Summer | |
| Fulgencio Obelmejias | Venezuela | Boxing | 1976 Summer | |
| Ernst Oberaigner | Austria | Alpine skiing | 1960 Winter | |
| Maria Oberbreyer | Athletics | 1948 Summer | |
| Norberto Oberburger | Italy | Weightlifting | 1980 Summer, 1984 Summer, 1988 Summer, 1992 Summer | |
| Sonja Oberem | Germany | Athletics | 1996 Summer, 2000 Summer | |
| Maksim Oberemko | Ukraine, Russia | Sailing | 1996 Summer, 2000 Summer, 2004 Summer, 2008 Summer, 2012 Summer, 2016 Summer | |
| Olena Oberemko | Ukraine | Basketball | 1996 Summer | |
| Hans-Sigfrid Oberer | Switzerland | Cross country skiing | 1964 Winter | |
| Karl-Heinz Oberfranz | East Germany | Road cycling | 1972 Summer | |
| Albert Öberg | Sweden | Athletics | 1912 Summer | |
| Carl-Göran Öberg | Ice hockey | 1960 Winter, 1964 Winter, 1968 Winter | |
| Eje Öberg | Sailing | 1988 Summer | |
| Elvira Öberg | Biathlon | 2022 Winter | |
| Erik Öberg [ Wikidata ] | Wrestling | 1912 Summer | |
| Hanna Öberg | Biathlon | 2018 Winter, 2022 Winter | |
| Hans Öberg | Ice hockey | 1952 Winter, 1956 Winter | |
| Helge Öberg | Diving | 1924 Summer, 1928 Summer | |
| Per Öberg | Handball | 1984 Summer | |
| Rune Öberg | Water polo | 1948 Summer | |
| Sigfrid Öberg | Ice hockey | 1928 Winter | |
| Thomas Öberg | Figure skating | 1980 Winter | |
| Christina Obergföll | Germany | Athletics | 2004 Summer, 2008 Summer, 2012 Summer, 2016 Summer | |
| Giulio Oberhammer | Italy | Ice hockey | 1956 Winter, 1964 Winter | |
| August Oberhauser | Switzerland | Football | 1924 Summer | |
| Josef Oberhauser | Austria | Bobsleigh | 1972 Winter | |
| Karin Oberhofer | Italy | Biathlon | 2010 Winter, 2014 Winter | |
| Ute Oberhoffner | East Germany | Luge | 1984 Winter, 1988 Winter | |
| Kurt Oberhöller | Austria | Bobsleigh | 1976 Winter, 1980 Winter | |
| Carla Oberholzer | South Africa | Road cycling | 2020 Summer | |
| Dallas Oberholzer | Skateboarding | 2020 Summer, 2024 Summer | |
| Henry Oberholzer | Great Britain | Artistic gymnastics | 1912 Summer | |
| Marlies Oberholzer | Switzerland | Alpine skiing | 1976 Winter | |
| Günter Oberhuber | Austria | Ice hockey | 1976 Winter | |
| Hans-Peter Oberhuber | West Germany | Speed skating | 1984 Winter, 1988 Winter | |
| Veronika Oberhuber | Italy | Luge | 1984 Winter, 1988 Winter | |
| Daniel Oberkofler | Austria | Ice hockey | 2014 Winter | |
| Fred Oberlander | Great Britain | Wrestling | 1948 Summer | |
| Phil Oberlander | Canada | 1964 Summer | |
| Emil Oberle | Germany | Football | 1912 Summer | |
| Ottmar Obermaier | Art competitions | 1928 Summer | |
| Mark Oberman | Australia | Water polo | 1992 Summer, 2000 Summer | |
| Paul Oberman | 1992 Summer | |
| Brigitte Obermoser | Austria | Alpine skiing | 1998 Winter, 2002 Winter | |
| Stephanie Obermoser | Shooting | 2012 Summer | |
| Beni Obermüller | Germany | Alpine skiing | 1952 Winter, 1956 Winter | |
| Georg Obermüller | Austria | Sailing | 1948 Summer | |
| Horst Obermüller | 1948 Summer | |
| David Obernosterer | Badminton | 2016 Summer | |
| Robert Oberrauch | Italy | Ice hockey | 1992 Winter, 1994 Winter, 1998 Winter | |
| Fritz Obersiebrasse | Germany | Athletics | 1964 Summer | |
| Swann Oberson | Switzerland | Marathon swimming | 2008 Summer, 2012 Summer | |
| Eugene Oberst | United States | Athletics | 1924 Summer | |
| Walter Oberste | Germany | 1956 Summer | |
| Christian Oberstolz | Italy | Luge | 2002 Winter, 2006 Winter, 2010 Winter, 2014 Winter | |
| Anastasia Oberstolz-Antonova | Russia, Italy | 2002 Winter, 2006 Winter | |
| Alex Obert | United States | Water polo | 2016 Summer, 2020 Summer, 2024 Summer | |
| Julia Obertas | Russia | Figure skating | 2006 Winter | |
| Giuliano Oberti | Italy | Sailing | 1928 Summer, 1936 Summer | |
| Massimo Oberti | 1928 Summer, 1936 Summer, 1956 Summer | |
| Fabricio Oberto | Argentina | Basketball | 1996 Summer, 2004 Summer, 2008 Summer | |
| Giorgio Oberweger | Italy | Athletics | 1936 Summer, 1948 Summer | |
| Myriam Oberwiler | Switzerland | Figure skating | 1984 Winter | |
| Edward Obewa | Uganda | Boxing | 1988 Summer | |
| Lodovico Obexer | Italy | Bobsleigh | 1924 Winter | |
| Wallace Obey | Liberia | Athletics | 1984 Summer | |
| Alex Obeysekere | Sri Lanka | Boxing | 1948 Summer | |
| Anton Obholzer | Great Britain | Rowing | 1988 Summer | |
| Rupert Obholzer | 1992 Summer, 1996 Summer | |
| Ashanti Obi | Nigeria | Athletics | 1972 Summer | |
| Christian Obi | Football | 1988 Summer | |
| Thomas Obi | Athletics | 1956 Summer | |
| Lenient Obia | Swimming | 2004 Summer | |
| Amarachi Obiajunwa | Wrestling | 2008 Summer, 2012 Summer | |
| José Obial | Philippines | Swimming | 1936 Summer | |
| Jerry Obiang | Gabon | Football | 2012 Summer | |
| EJ Obiena | Philippines | Athletics | 2020 Summer, 2024 Summer | |
| Mercy Obiero | Kenya | Weightlifting | 2012 Summer | |
| Maiko Obikawa | Japan | Ice hockey | 1998 Winter | |
| Michael Obiku | Nigeria | Football | 1988 Summer | |
| Francis Obikwelu | Nigeria, Portugal | Athletics | 1996 Summer, 2000 Summer, 2004 Summer, 2008 Summer | |
| Kenichi Obinata | Japan | Rowing | 1996 Summer | |
| Victor Obinna | Nigeria | Football | 2008 Summer | |
| Carola Vila Obiols [ Wikidata ] | Andorra | Cross country skiing | 2022 Winter | |
| Juliana Obiong | Equatorial Guinea | Athletics | 1988 Summer, 1996 Summer | |
| Jacob Martins Obiorah | Nigeria | Taekwondo | 2004 Summer | |
| Hellen Obiri | Kenya | Athletics | 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Ryuichi Obitani | Japan | Figure skating | 1932 Winter | |
| Gábor Obitz | Hungary | Football | 1924 Summer | |
| Aleksandrs Obižajevs | Latvia | Athletics | 1992 Summer, 1996 Summer | |
| Natalie Obkircher | Italy | Luge | 1992 Winter, 1994 Winter, 1998 Winter, 2002 Winter | |
| Lenart Oblak | Slovenia | Biathlon | 2018 Winter | |
| Halyna Obleshchuk | Ukraine | Athletics | 2016 Summer | |
| Helmut Oblinger | Austria | Canoe slalom | 1996 Summer, 2000 Summer, 2004 Summer, 2008 Summer, 2012 Summer | |
| Violetta Oblinger-Peters | 2000 Summer, 2004 Summer, 2008 Summer | |
| Emmanuel Oblitey | Ghana | Football | 1964 Summer | |
| Tadeusz Obłój | Poland | Ice hockey | 1972 Winter, 1976 Winter, 1980 Winter | |
| Yelena Oblova | Russia, Croatia | Sailing | 2012 Summer, 2020 Summer, 2024 Summer | |
| Aleksey Obmochaev | Russia | Volleyball | 2012 Summer | |
| Osaro Obobaifo | Nigeria | Football | 1988 Summer | |
| Clement Obojememe | 1968 Summer | |
| Oleksandr Obolonchyk | Ukraine | Luge | 2014 Winter, 2018 Winter | |
| Seiko Obonai | Japan | Athletics | 1964 Summer | |
| Amador Obordo | Philippines | Basketball | 1936 Summer | |
| Ryszard Oborski | Poland | Canoe sprint | 1976 Summer, 1980 Summer | |
| Blessing Oborududu | Nigeria | Wrestling | 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Delmas Obou | Italy | Bobsleigh | 2022 Winter | |
| Bendere Oboya | Australia | Athletics | 2020 Summer | |
| Anja Obradović | Serbia | Judo | 2020 Summer | |
| Dragan Obradović | Yugoslavia | Rowing | 1980 Summer | |
| Iva Obradović | Serbia | 2008 Summer | |
| Paulo Obradović | Croatia | Water polo | 2012 Summer, 2020 Summer | |
| Saša Obradović | Serbia and Montenegro | Basketball | 1996 Summer, 2000 Summer | |
| Željko Obradović | Yugoslavia | 1988 Summer | |
| Stjepan Obran | Handball | 1980 Summer | |
| Daria Obratov | Croatia | Luge | 2018 Winter | |
| Marja Obrębska | Poland | Art competitions | 1932 Summer | |
| Heidi Obrecht | Switzerland | Alpine skiing | 1964 Winter | |
| Paul Obrecht [ Wikidata ] | France | Artistic gymnastics | 1900 Summer | |
| Theres Obrecht | Switzerland | Alpine skiing | 1964 Winter | |
| Graeme Obree | Great Britain | Track cycling | 1996 Summer | |
| Darlenys Obregón | Colombia | Athletics | 2008 Summer, 2012 Summer | |
| Juan Carlos Obregón | Honduras | Football | 2020 Summer | |
| Patricia Obregón | Mexico | Swimming | 1968 Summer | |
| Patricia Obregón | Costa Rica | Archery | 1992 Summer | |
| Constantin Obreja | Romania | Bobsleigh | 1980 Winter | |
| Grigore Obreja | Canoe sprint | 1988 Summer, 1996 Summer | |
| Rudel Obreja | Boxing | 1984 Summer | |
| Hannes Obreno | Belgium | Rowing | 2016 Summer | |
| Peter Obresa | West Germany | Ice hockey | 1988 Winter | |
| Lyuben Obretenov | Bulgaria | Artistic gymnastics | 1936 Summer | |
| Alex O'Brien | United States | Tennis | 2000 Summer | |
| Anne O'Brien | Athletics | 1928 Summer, 1936 Summer | |
| Brittany O'Brien | Australia | Diving | 2016 Summer | |
| Cathy O'Brien | United States | Athletics | 1988 Summer, 1992 Summer | |
| Christy O'Brien | Ireland | Rowing | 1976 Summer, 1980 Summer | |
| Colm O'Brien | Fencing | 1968 Summer | |
| Connor O'Brien | Great Britain, Estonia | Alpine skiing | 1984 Winter, 1994 Winter | |
| Cory O'Brien | Australia | Wrestling | 1996 Summer, 2000 Summer | |
| Dan O'Brien | United States | Athletics | 1996 Summer | |
| Danielle O'Brien | Australia | Figure skating | 2014 Winter | |
| Danny O'Brien | Ireland | Boxing | 1960 Summer | |
| David O'Brien | Sailing | 2000 Summer | |
| David O'Brien | Great Britain | Swimming | 2004 Summer | |
| Denise O'Brien | Australia | Fencing | 1956 Summer | |
| Dermod O'Brien | Ireland | Art competitions | 1928 Summer | |
| Edward O'Brien | United States | Athletics | 1936 Summer | |
| Flora Vere O'Brien | Ireland | Art competitions | 1948 Summer | |
| Henry O'Brien | United States | Road cycling | 1928 Summer, 1932 Summer | |
| Ian O'Brien | Australia | Swimming | 1964 Summer, 1968 Summer | |
| Jay O'Brien | United States | Bobsleigh | 1928 Winter, 1932 Winter | |
| James O'Brien | Canada | Athletics | 1948 Summer | |
| John O'Brien | New Zealand | Rowing | 1952 Summer | |
| John O'Brien | United States | Football | 2000 Summer | |
| John O'Brien | Australia | Water polo | 1956 Summer, 1960 Summer | |
| Joseph O'Brien | Rowing | 2020 Summer, 2024 Summer | |
| Kate O'Brien | Canada | Track cycling | 2016 Summer | |
| Kelland O'Brien | Australia | 2020 Summer, 2024 Summer | |
| Kerry O'Brien | Athletics | 1968 Summer, 1972 Summer | |
| Kristine O'Brien | United States | Rowing | 2020 Summer | |
| Leah O'Brien | Softball | 1996 Summer, 2000 Summer, 2004 Summer | |
| Leonard O'Brien | Field hockey | 1932 Summer, 1936 Summer | |
| Liam O'Brien | Ireland | Athletics | 1984 Summer | |
| Michael O'Brien | Fencing | 1992 Summer | |
| Mick O'Brien | Australia | Boxing | 1972 Summer | |
| Mike O'Brien | United States | Swimming | 1984 Summer | |
| Nathaniel O'Brien | Canada | 2004 Summer | |
| Nina O'Brien | United States | Alpine skiing | 2022 Winter | |
| Paris O'Brien | China | Ice hockey | 2022 Winter | |
| Parry O'Brien | United States | Athletics | 1952 Summer, 1956 Summer, 1960 Summer, 1964 Summer | |
| Paul O'Brien | New Zealand | Equestrian eventing | 2000 Summer | |
| Robert O'Brien | United States | Canoe sprint | 1956 Summer, 1960 Summer | |
| Shane O'Brien | New Zealand | Rowing | 1984 Summer | |
| Shaun O'Brien | Australia | Track cycling | 1992 Summer | |
| Spencer O'Brien | Canada | Snowboarding | 2014 Winter, 2018 Winter | |
| Terence O'Brien | Great Britain | Rowing | 1928 Summer | |
| Terry O'Brien | United States | Luge | 1972 Winter, 1976 Winter | |
| Wesley O'Brien | Australia | Wrestling | 1968 Summer | |
| Theodor Obrietan | Austria | Rowing | 1948 Summer | |
| Christian Obrist | Italy | Athletics | 2008 Summer | |
| Jakub Obrovský | Czechoslovakia | Art competitions | 1924 Summer, 1932 Summer, 1948 Summer | |
| Hugues Obry | France | Fencing | 2000 Summer, 2004 Summer | |
| Cecily O'Bryen | Great Britain | Diving | 1924 Summer | |
| Alfred Obschernikat | Germany | Water polo | 1956 Summer | |
| Werner Obschernikat | West Germany | 1976 Summer, 1984 Summer, 1988 Summer | |
| Andreas Obst | Germany | Basketball | 2020 Summer, 2024 Summer | |
| Herbert Obst | Canada | Fencing | 1972 Summer | |
| Marie-Therese Obst | Norway | Athletics | 2024 Summer | |
| Michael Obst | Germany | Rowing | 1960 Summer | |
| Jaroslav Obšut | Slovakia | Ice hockey | 2002 Winter | |
| Igor Obukhov | Belarus | Cross country skiing | 1994 Winter | |
| Roselidah Obunaga | Kenya | Volleyball | 2000 Summer, 2004 Summer | |
| Harold Obunga | Boxing | 1988 Summer | |
| Donald Obwoge | Judo | 1992 Summer | |
| Maisiba Obwoge | Wrestling | 1988 Summer | |
| Tzipora Obziler | Israel | Tennis | 2008 Summer | |
| Miki Oca | Spain | Water polo | 1992 Summer, 1996 Summer | |
| Con O'Callaghan | Ireland | Athletics | 1928 Summer | |
| Mollie O'Callaghan | Australia | Swimming | 2020 Summer, 2024 Summer | |
| Pat O'Callaghan | Ireland | Athletics | 1928 Summer, 1932 Summer | |
| Xavier O'Callaghan | Spain | Handball | 2000 Summer, 2004 Summer | |
| Jack O'Callahan | United States | Ice hockey | 1980 Winter | |
| Daiana Ocampo | Argentina | Athletics | 2024 Summer | |
| Ed Ocampo | Philippines | Basketball | 1960 Summer, 1968 Summer, 1972 Summer | |
| Felix Ocampo | Boxing | 1964 Summer | |
| Gustavo Ocampo | Peru | Swimming | 1964 Summer | |
| Hernando R. Ocampo | Philippines | Art competitions | 1948 Summer | |
| Jahir Ocampo | Mexico | Diving | 2016 Summer | |
| Mauricio Ocampo | Swimming | 1960 Summer | |
| Raymond Ocampo | Philippines | Luge | 1988 Winter | |
| Walter Ocampo | Mexico | Swimming | 1952 Summer, 1956 Summer | |
| Luis Ocaña | Cuba | Wrestling | 1980 Summer | |
| José Ocando | Venezuela | Weightlifting | 2008 Summer | |
| Asunción Ocasio | Puerto Rico | Taekwondo | 2008 Summer | |
| Karina Ocasio | Volleyball | 2016 Summer | |
| Diego Occhiuzzi | Italy | Fencing | 2008 Summer, 2012 Summer, 2016 Summer | |
| José Ocejo | Spain | Sailing | 1960 Summer | |
| Glenn Ochal | United States | Rowing | 2012 Summer, 2016 Summer | |
| Jorem Ochana | Uganda | Athletics | 1964 Summer | |
| Hendrik Ochel | Germany | Handball | 1992 Summer | |
| Oleh Ocheretko | Ukraine | Football | 2024 Summer | |
| Hiromasa Ochiai | Japan | Field hockey | 2020 Summer | |
| Masayoshi Ochiai | Athletics | 1932 Summer | |
| Osamu Ochiai | Shooting | 1960 Summer, 1964 Summer | |
| Tomoya Ochiai | 3x3 basketball | 2020 Summer | |
| Isabella Ochichi | Kenya | Athletics | 2004 Summer | |
| Diana Ochieng | Rugby sevens | 2020 Summer | |
| Kennedy Ochieng | Athletics | 1996 Summer, 2000 Summer | |
| Pius Ochieng | Weightlifting | 1984 Summer, 1988 Summer | |
| Sofya Ochigava | Russia | Boxing | 2012 Summer | |
| Tsend-Ayuushiin Ochirbat | Mongolia | Judo | 2000 Summer, 2004 Summer | |
| Dashzevegiin Ochirsükh | Cross country skiing | 1998 Winter | |
| Erdene-Ochiryn Ochirsüren | 2006 Winter, 2010 Winter | |
| Bruno Ochman | Canada | Wrestling | 1956 Summer | |
| Łucja Ochmańska | Poland | Artistic gymnastics | 1968 Summer | |
| Nadya Ochner | Italy | Snowboarding | 2014 Winter, 2018 Winter, 2022 Winter | |
| Guillermo Ochoa | Mexico | Football | 2020 Summer | |
| Héctor Ochoa | Argentina | 1964 Summer | |
| Jefferson Ochoa | Colombia | Taekwondo | 2020 Summer | |
| José Ochoa | Venezuela | Wrestling | 1996 Summer | |
| Luis Ochoa | Colombia | Judo | 1988 Summer | |
| Manuel Ochoa | Spain | Canoe slalom | 2024 Summer | |
| Miguel Ángel Ochoa | Football | 1968 Summer | |
| Omar Ochoa | Guatemala | Road cycling | 1996 Summer | |
| Elly Ochola | Kenya | Boxing | 2020 Summer | |
| Prestina Ochonogor | Nigeria | Athletics | 2024 Summer | |
| Elli Ochowicz | United States | Speed skating | 2002 Winter, 2006 Winter, 2010 Winter | |
| Jim Ochowicz | Track cycling | 1972 Summer | |
| Deborah Ochs | Archery | 1988 Summer | |
| Jacques Ochs | Belgium | Fencing | 1912 Summer | |
| Pierre Ochs | France | Freestyle skiing | 2006 Winter, 2010 Winter | |
| Ochumba Lubandji | Zambia | Football | 2020 Summer, 2024 Summer | |
| Borislav Ochushki | Bulgaria | Cross country skiing | 1964 Winter | |
| Emil Ochyra | Poland | Fencing | 1960 Summer, 1964 Summer, 1968 Summer | |
| Hannes Ocik | Germany | Rowing | 2016 Summer, 2020 Summer | |
| Eddie Ockenden | Australia | Field hockey | 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Corrine Ockhuijsen | Netherlands | Softball | 1996 Summer | |
| Christa Öckl | West Germany | Archery | 1988 Summer | |
| Franc Očko | Yugoslavia | Judo | 1980 Summer, 1984 Summer | |
| Norberto Oconer | Philippines | Road cycling | 1988 Summer, 1992 Summer | |
| Alex O'Connell | Great Britain | Fencing | 2008 Summer | |
| Brendan O'Connell | Ireland | Canoe sprint | 1972 Summer, 1976 Summer | |
| Carlos O'Connell | Athletics | 1988 Summer | |
| James O'Connell | United States | 1908 Summer | |
| Jessica O'Connell | Canada | 2016 Summer | |
| Leo O'Connell | United States | Football | 1904 Summer | |
| Les O'Connell | New Zealand | Rowing | 1984 Summer | |
| Malcolm O'Connell | Great Britain | Swimming | 1972 Summer | |
| Adrian O'Connor | Ireland | 1996 Summer | |
| Andrew O'Connor | United States | Art competitions | 1928 Summer | |
| Ann O'Connor | Ireland | Swimming | 1968 Summer, 1972 Summer | |
| Austin O'Connor | Equestrian eventing | 2000 Summer, 2008 Summer, 2020 Summer, 2024 Summer | |
| Ben O'Connor | Australia | Road cycling | 2024 Summer | |
| Caroline O'Connor | Great Britain | Rowing | 2008 Summer, 2012 Summer | |
| Cian O'Connor | Ireland | Equestrian jumping | 2004 Summer, 2012 Summer, 2020 Summer, 2024 Summer | |
| Colleen O'Connor | United States | Figure skating | 1976 Winter | |
| Coralie O'Connor | Swimming | 1952 Summer | |
| Daniel O'Connor | Athletics | 1984 Summer | |
| David O'Connor | Equestrian eventing | 1996 Summer, 2000 Summer | |
| Debra O'Connor | Trinidad and Tobago | Badminton | 1996 Summer | |
| Denise O'Connor | United States | Fencing | 1964 Summer, 1976 Summer | |
| Finn O'Connor | New Zealand | Canoe sprint | 1992 Summer | |
| Frank O'Connor | Ireland | Basketball | 1948 Summer | |
| Fred O'Connor | United States | Football | 1924 Summer | |
| Jeremy O'Connor | Zimbabwe | Sailing | 1980 Summer | |
| John O'Connor | Ireland | Athletics | 1924 Summer | |
| Joseph O'Connor | Water polo | 1928 Summer | |
| Karen O'Connor | United States | Equestrian eventing | 1988 Summer, 1996 Summer, 2000 Summer, 2008 Summer, 2012 Summer | |
| Kate O'Connor | Ireland | Athletics | 2024 Summer | |
| Larry O'Connor | Canada | 1936 Summer | |
| Lauren O'Connor [ Wikidata ] | United States | Rowing | 2024 Summer | |
| Mary O'Connor | New Zealand | Athletics | 1984 Summer | |
| Mary Anne O'Connor | United States | Basketball | 1976 Summer | |
| Matthew O'Connor | Great Britain | Swimming | 1992 Summer | |
| Michael O'Connor | Ireland | Water polo | 1924 Summer, 1928 Summer | |
| Patrick O'Connor | Jamaica | Athletics | 1992 Summer | |
| Patrick O'Connor | United States | Art competitions | 1928 Summer | |
| Paul O'Connor | Ireland | Cross country skiing | 2002 Winter | |
| Robin O'Connor | Zimbabwe | Sailing | 1980 Summer | |
| Roderic O'Connor | United States | Art competitions | 1928 Summer | |
| Seamus O'Connor | Ireland | Snowboarding | 2014 Winter, 2018 Winter, 2022 Winter | |
| Seán O'Connor | Wrestling | 1960 Summer, 1964 Summer | |
| Shane O'Connor | Alpine skiing | 2010 Winter | |
| Siobhan-Marie O'Connor | Great Britain | Swimming | 2012 Summer, 2016 Summer | |
| Susan O'Connor | Canada | Curling | 2010 Winter | |
| Tony O'Connor | Ireland | Rowing | 1996 Summer, 2000 Summer | |
| Wally O'Connor | United States | Swimming, Water polo | 1924 Summer, 1928 Summer, 1932 Summer, 1936 Summer | |
| William O'Connor | Fencing | 1904 Summer | |
| Emma O'Croinin | Canada | Swimming | 2024 Summer | |
| Rezza Octavia | Indonesia | Archery | 2024 Summer | |
| Daniel Octobre | France | Art competitions | 1928 Summer | |
| Ernst Ocwirk | Austria | Football | 1948 Summer | |
| Chieko Oda | Japan | Artistic gymnastics | 1968 Summer | |
| Katsumi Oda | Volleyball | 1976 Summer | |
| Mikio Oda | Athletics | 1924 Summer, 1928 Summer, 1932 Summer | |
| Nobunari Oda | Figure skating | 2010 Winter | |
| Takuro Oda | Speed skating | 2018 Winter, 2022 Winter | |
| Yuka Oda | Ice hockey | 1998 Winter | |
| Tevfik Odabaşı | Turkey | Wrestling | 2004 Summer, 2008 Summer | |
| Yukio Odagiri | Japan | Boxing | 1976 Summer | |
| Emiko Odaka | Volleyball | 1984 Summer | |
| Makoto Odakura | Triathlon | 2020 Summer, 2024 Summer | |
| Clifford Odame | Ghana | Football | 1972 Summer | |
| Douglas Odame | Boxing | 1984 Summer | |
| Charles Addo Odametey | Football | 1964 Summer, 1968 Summer | |
| Kristy Odamura | Canada | Softball | 2000 Summer, 2004 Summer | |
| George O'Day | United States | Sailing | 1960 Summer | |
| Ganbaataryn Odbayar | Mongolia | Judo | 2016 Summer | |
| Frank Odberg | Belgium | Rowing | 1900 Summer | |
| John Odde | Great Britain | Athletics | 1924 Summer | |
| Olav Odden | Norway | Cross country skiing, Nordic combined | 1948 Winter | |
| Brian Oddie | Great Britain | Athletics | 1928 Summer | |
| Donnacha O'Dea | Ireland | Swimming | 1968 Summer | |
| Viola Odebrecht | Germany | Football | 2004 Summer | |
| Henrik Ødegaard | Norway | Ice hockey | 2014 Winter, 2018 Winter | |
| Reidar Ødegaard | Cross country skiing | 1928 Winter | |
| Hans Petter Ødegård | Road cycling | 1984 Summer | |
| Segun Odegbami | Nigeria | Football | 1980 Summer | |
| Wole Odegbami | 1988 Summer | |
| Antonín Odehnal | Czechoslovakia | Art competitions | 1932 Summer | |
| Erik Odelberg [ Wikidata ] | Sweden | Shooting | 1912 Summer | |
| Tega Odele | Nigeria | Athletics | 2016 Summer | |
| Vicyohandri Odelín | Cuba | Baseball | 2004 Summer, 2008 Summer | |
| Eric O'Dell | Canada | Ice hockey | 2018 Winter, 2022 Winter | |
| Peter Odemwingie | Nigeria | Football | 2008 Summer | |
| Beverly Oden | United States | Volleyball | 1996 Summer | |
| Elaina Oden | 1992 Summer, 1996 Summer | |
| Kim Oden | 1988 Summer, 1992 Summer | |
| Joop Odenthal | Netherlands | Football | 1952 Summer | |
| Marc Odenthal | Germany | Judo | 2016 Summer | |
| Tjaša Oder | Slovenia | Swimming | 2012 Summer, 2016 Summer | |
| Chris Odera | Kenya | Boxing | 1988 Summer | |
| Adolf Odermatt | Switzerland | Alpine skiing | 1948 Winter | |
| Marco Odermatt | 2022 Winter | |
| Ladislao Odescalchi | Italy | Shooting | 1952 Summer | |
| Alex Odhiambo | Uganda | Boxing | 1964 Summer, 1968 Summer | |
| Billy Odhiambo | Kenya | Rugby sevens | 2016 Summer, 2020 Summer | |
| Joyce Odhiambo | Athletics | 1988 Summer | |
| Peter Odhiambo | Uganda | Boxing | 1972 Summer | |
| Peter Odhiambo | 1980 Summer | |
| Peter Odhiambo | Kenya | 1996 Summer | |
| Peter Paul Odhiambo | Uganda | 1960 Summer, 1964 Summer | |
| Shadrach Odhiambo | Sweden | 1980 Summer, 1984 Summer | |
| Roy Odhier | Kenya | Field hockey | 1988 Summer | |
| Elizbar Odikadze | Georgia | Wrestling | 2016 Summer, 2020 Summer | |
| Alisher Odilov | Uzbekistan | Football | 2024 Summer | |
| Cécile Odin | France | Road cycling | 1984 Summer, 1988 Summer | |
| Dan Odindo [ Wikidata ] | Uganda | Boxing | 1988 Summer | |
| George Olwande Odindo | Kenya | 2000 Summer | |
| Meryeta O'Dine | Canada | Snowboarding | 2022 Winter | |
| Árni Óðinsson | Iceland | Alpine skiing | 1976 Winter | |
| Moses Odion | Nigeria | Boxing | 1992 Summer | |
| Edidiong Odiong | Bahrain | Athletics | 2016 Summer | |
| Lilian Odira | Kenya | 2024 Summer | |
| Nduka Odizor | Nigeria | Tennis | 1988 Summer | |
| Vadis Odjidja-Ofoe | Belgium | Football | 2008 Summer | |
| Batjargalyn Odkhüü | Mongolia | Judo | 2000 Summer, 2004 Summer | |
| Josef Odložil | Czechoslovakia | Athletics | 1964 Summer, 1968 Summer | |
| Jayhan Odlum-Smith | Saint Lucia | Swimming | 2024 Summer | |
| Ture Ödlund | Sweden | Curling | 1924 Winter | |
| Åke Ödmark | Athletics | 1936 Summer | |
| Maxim Odnodvortsev | Kazakhstan | Cross country skiing | 2002 Winter, 2006 Winter | |
| Violet Odogwu | Nigeria | Athletics | 1968 Summer | |
| Lamar Odom | United States | Basketball | 2004 Summer | |
| Badrakhyn Odonchimeg | Mongolia | Wrestling | 2008 Summer | |
| James Odongo | Uganda | Athletics | 1964 Summer | |
| Patrick Odongo | Kenya | Rugby sevens | 2024 Summer | |
| Katie O'Donnell Bam | United States | Field hockey | 2012 Summer, 2016 Summer | |
| Ann O'Donnell | Fencing | 1972 Summer, 1976 Summer | |
| Carl O'Donnell | New Zealand | Swimming | 2012 Summer | |
| Christopher O'Donnell | Ireland | Athletics | 2020 Summer, 2024 Summer | |
| Jennifer O'Donnell | United States | Archery | 1992 Summer | |
| Marty O'Donnell | Canada | Boxing | 1992 Summer | |
| Peter O'Donnell | Australia | Sailing | 1964 Summer | |
| Tela O'Donnell | United States | Wrestling | 2004 Summer | |
| William O'Donnell | Great Britain | Swimming | 1960 Summer | |
| Peter O'Donoghue | New Zealand | Athletics | 1984 Summer | |
| Shane O'Donoghue | Ireland | Field hockey | 2016 Summer, 2024 Summer | |
| Éamon O'Donohoe | Equestrian jumping | 1960 Summer | |
| Thomas O'Donahue | Great Britain | Athletics | 1912 Summer | |
| Gary O'Donovan | Ireland | Rowing | 2016 Summer | |
| Kevin O'Donovan | Basketball | 1948 Summer | |
| Paul O'Donovan | Rowing | 2016 Summer, 2020 Summer, 2024 Summer | |
| Andrea Ódor | Hungary | Badminton | 1996 Summer | |
| Gabriel Odor | Austria | Speed skating | 2022 Winter | |
| Lajos Ódor | Hungary | Rowing | 1980 Summer | |
| Nick Odore | Kenya | Boxing | 1992 Summer | |
| Eva Ódorová | Slovakia | Table tennis | 2008 Summer, 2016 Summer | |
| Matt O'Dowd | Great Britain | Athletics | 2004 Summer | |
| Jade O'Dowda | 2024 Summer | |
| Fidel Odreman | Venezuela | Boxing | 1960 Summer | |
| Antal Odri | Hungary | Athletics | 1928 Summer | |
| Kauldi Odriozola | Spain | Handball | 2024 Summer | |
| Mikel Odriozola | Athletics | 2000 Summer, 2008 Summer, 2012 Summer | |
| Francisco Oduardo | Cuba | Boxing | 1968 Summer | |
| Divine Oduduru | Nigeria | Athletics | 2016 Summer, 2020 Summer | |
| Muizat Ajoke Odumosu | 2008 Summer, 2012 Summer | |
| Abiola Odumosu | Table tennis | 1992 Summer | |
| Emmanuel Oduol | Kenya | Field hockey | 1984 Summer | |
| Michael Oduor | Judo | 1992 Summer | |
| Muyiwa Odusanya | Nigeria | Weightlifting | 1988 Summer | |
| Johnny Oduya | Sweden | Ice hockey | 2010 Winter, 2014 Winter | |
| Dave Odwell | Great Britain | Boxing | 1976 Summer | |
| James Odwori | Uganda | 1972 Summer | |
| Adrian O'Dwyer | Ireland | Athletics | 2004 Summer | |
| Lyubov Odynokova | Soviet Union | Handball | 1976 Summer, 1980 Summer | |
| Lisa Odynski | United States | Snowboarding | 2002 Winter | |
| Hideo Oe | Japan | Rowing | 1964 Summer | |
| Hikaru Ōe | Snowboarding | 2018 Winter | |
| Sueo Ōe | Athletics | 1936 Summer | |
| Gerhard Oechsle | West Germany | Bobsleigh | 1984 Winter | |
| Chris Oeding | United States | Water polo | 1996 Summer, 2000 Summer | |
| Henry Oehler | Handball | 1936 Summer | |
| Otto Oehler | 1936 Summer | |
| Peter Oehler [ Wikidata ] | Germany | Wrestling | 1912 Summer | |
| Harald Oehme | East Germany | Speed skating | 1976 Winter | |
| Herbert Oehmichen | United States | Handball | 1936 Summer | |
| Egon Oehri | Liechtenstein | Athletics | 1960 Summer | |
| Alfons Oehy | Switzerland | Swimming | 1952 Summer | |
| Oei Hok Tiang | Indonesia | Boxing | 1960 Summer | |
| Oei Liana | Chinese Taipei | Swimming | 1968 Summer | |
| Hernán Oelckers | Chile | Alpine skiing | 1948 Winter | |
| Moritz Oeler | Germany | Water polo | 2008 Summer | |
| Jürgen Oelke | Rowing | 1964 Summer | |
| Olga Oelkers | Fencing | 1928 Summer, 1936 Summer | |
| Karsten Oelsch | Artistic gymnastics | 1996 Summer | |
| Trent Oeltjen | Australia | Baseball | 2004 Summer | |
| Thijsje Oenema | Netherlands | Speed skating | 2010 Winter | |
| Walter von Oepen | West Germany | Handball | 1976 Summer | |
| Brigitte Oertel | Fencing | 1972 Summer, 1976 Summer | |
| Rudi Oertel | Germany | Diving | 1960 Summer | |
| Waltraud Oertel | 1960 Summer | |
| Al Oerter | United States | Athletics | 1956 Summer, 1960 Summer, 1964 Summer, 1968 Summer | |
| Brigitte Oertli | Switzerland | Alpine skiing | 1984 Winter, 1988 Winter | |
| Jennifer Oeser | Germany | Athletics | 2008 Summer, 2012 Summer, 2016 Summer | |
| Østen Østensen | Norway | Shooting | 1912 Summer, 1920 Summer | |
| Marlies Oester | Switzerland | Alpine skiing | 2002 Winter | |
| Kåre Østerdal | Norway | Cross country skiing, Nordic combined | 1948 Winter | |
| Dieter Oesterlen | Germany | Art competitions | 1936 Summer | |
| Friedrich von Oesterley [ Wikidata ] | Equestrian dressage | 1912 Summer | |
| Johannes Oesterling | Swimming | 2004 Summer | |
| Rolf Österreich | East Germany | Figure skating | 1976 Winter | |
| Elisabeth Oestreich | Germany | Athletics | 1928 Summer | |
| Oliver Oetke | Beach volleyball | 2000 Summer | |
| Elena Oetling | Mexico | Sailing | 2020 Summer, 2024 Summer | |
| Saskia Oettinghaus [ Wikidata ] | Germany | Diving | 2024 Summer | |
| Manfred Oettl Reyes | Peru | Alpine skiing | 2010 Winter, 2014 Winter | |
| Ornella Oettl Reyes | 2010 Winter, 2014 Winter, 2022 Winter | |
| Patrick Oeuvrard | France | Sailing | 1976 Summer | |
| Egbert van 't Oever | Netherlands | Speed skating | 1952 Winter, 1956 Winter | |
| Maria Oeyen | Belgium | Swimming | 1948 Summer | |
| Derek O'Farrell | Canada | Rowing | 2012 Summer | |
| Raisa O'Farrill Bolanos | Cuba | Volleyball | 1996 Summer | |
| Yordan O'Farrill | Athletics | 2016 Summer | |
| Steffi Ofenböck | Austria | Handball | 2000 Summer | |
| Gil Ofer | Israel | Judo | 2000 Summer | |
| Katharina Offel | Ukraine | Equestrian jumping | 2008 Summer, 2012 Summer | |
| Patricia Offel | Ghana | Table tennis | 1988 Summer | |
| Helga Offen | East Germany | Volleyball | 1976 Summer | |
| Franz Offenberger | Austria | Speed skating | 1952 Winter, 1956 Winter, 1960 Winter | |
| Pieter Offens | Netherlands | Rowing | 1972 Summer | |
| Ben Offereins | Australia | Athletics | 2012 Summer | |
| Tinka Offereins | Netherlands | Rowing | 2024 Summer | |
| Hendrik Offerhaus | 1900 Summer | |
| Jill Officer | Canada | Curling | 2014 Winter | |
| Karoline Offigstad Knotten | Norway | Biathlon | 2022 Winter | |
| Cecilia Offiong | Nigeria | Table tennis | 2004 Summer, 2008 Summer | |
| Raymond Offner | France | Basketball | 1948 Summer | |
| Gentle Offoin | Nigeria | Swimming | 2000 Summer | |
| Theresa Offredy | Great Britain | Fencing | 1964 Summer | |
| Favour Ofili | Nigeria | Athletics | 2024 Summer | |
| Ofisa Ofisa | Samoa | Weightlifting | 1996 Summer, 2000 Summer | |
| Taveuni Ofisa | 1988 Summer | |
| Kerry O'Flaherty | Ireland | Athletics | 2016 Summer | |
| Stephen O'Flaherty | Canoe slalom | 1996 Summer | |
| Anna O'Flanagan | Field hockey | 2020 Summer | |
| Katrin Ofner | Austria | Freestyle skiing | 2010 Winter, 2014 Winter, 2018 Winter, 2022 Winter | |
| Klaus Ofner | Nordic combined | 1988 Winter, 1992 Winter | |
| Sebastian Ofner | Tennis | 2024 Summer | |
| Zacharia Ofri | Israel | Basketball | 1952 Summer | |
| Julie Ofsoski | New Zealand | 2000 Summer, 2004 Summer | |
| Kari Ofstad | Norway | Canoe sprint | 1984 Summer | |
| Jens Lurås Oftebro | Nordic combined | 2022 Winter | |
| Stine Oftedal Dahmke | Handball | 2016 Summer, 2020 Summer, 2024 Summer | |
| Augustine Ofuokwu | Nigeria | Football | 1968 Summer | |
| Augustus Oga | Kenya | Boxing | 1984 Summer | |
| Yuko Oga | Japan | Basketball | 2004 Summer | |
| Douglas Ogada | Uganda | Boxing | 1968 Summer | |
| Faith Ogallo | Kenya | Taekwondo | 2020 Summer | |
| George Ogan | Nigeria | Athletics | 1964 Summer | |
| İsmail Ogan | Turkey | Wrestling | 1960 Summer, 1964 Summer | |
| Alexander Ogando | Dominican Republic | Athletics | 2020 Summer, 2024 Summer | |
| Khoren Oganesian | Soviet Union | Football | 1980 Summer | |
| Alina Oganesyan | Germany | Rhythmic gymnastics | 2024 Summer | |
| Albert Oganezov | Soviet Union | Handball | 1972 Summer | |
| Sanasar Oganisyan | Wrestling | 1980 Summer | |
| Jolanta Ogar-Hill | Poland, Austria | Sailing | 2012 Summer, 2016 Summer, 2020 Summer | |
| Lenford O'Garro | Saint Vincent and the Grenadines | Athletics | 1992 Summer | |
| Ayumi Ogasawara | Japan | Curling | 2002 Winter, 2006 Winter, 2014 Winter | |
| Liliko Ogasawara | United States | Judo | 1996 Summer | |
| Michihiro Ogasawara | Japan | Baseball | 2004 Summer | |
| Miki Ogasawara | Speed skating | 1994 Winter | |
| Tadashi Ogasawara | Track cycling | 1976 Summer | |
| Tsuneo Ogasawara | Rowing | 1964 Summer | |
| Yoshiaki Ogasawara | Track cycling | 1976 Summer | |
| Akari Ogata | Judo | 2012 Summer | |
| Atsunobu Ogata | Canoe sprint | 1976 Summer | |
| Shigeo Ogata | Swimming | 1984 Summer, 1988 Summer, 1992 Summer | |
| Tsuyoshi Ogata | Athletics | 2008 Summer | |
| Carlton Ogawa | Canada | Rowing | 1956 Summer | |
| Daiki Ogawa [ Wikidata ] | Japan | Athletics | 2024 Summer | |
| Hiroshi Ogawa | Cross country skiing | 1968 Winter | |
| Jiro Ogawa | Ice hockey | 1964 Winter | |
| Kiyoko Ogawa | Athletics | 1964 Summer | |
| Masaru Ogawa | Figure skating | 1984 Winter | |
| Mieko Ogawa | Luge | 1976 Winter | |
| Naoya Ogawa | Judo | 1992 Summer, 1996 Summer | |
| Naoyuki Ogawa | Sailing | 1988 Summer | |
| Rika Ogawa | Field hockey | 2024 Summer | |
| Satoshi Ogawa | Fencing | 2008 Summer | |
| Roman Ogaza | Poland | Football | 1976 Summer | |
| Samuel Ogazi | Nigeria | Athletics | 2024 Summer | |
| Ruth Ogbeifo | Weightlifting | 2000 Summer | |
| Chiaka Ogbogu | United States | Volleyball | 2020 Summer, 2024 Summer | |
| Julie Ogborn | Guam | Athletics | 1988 Summer | |
| Ben Ogden | United States | Cross country skiing | 2022 Winter | |
| David Ogden | Great Britain | Wrestling | 1988 Summer | |
| Best Ogedegbe | Nigeria | Football | 1980 Summer | |
| Renée Oger | France | Artistic gymnastics | 1928 Summer | |
| Yves Oger | Rowing | 1972 Summer | |
| Aritatsu Ogi | Japan | Football | 1964 Summer, 1968 Summer | |
| Andy Ogide | Nigeria | Basketball | 2016 Summer | |
| Daichi Ogihara [ Wikidata ] | Japan | Water polo | 2024 Summer | |
| Takahiro Ogihara | Football | 2012 Summer | |
| John Ogiltree | Canada | Baseball | 2004 Summer | |
| Charles Ogilvie | Jamaica | Sailing | 1968 Summer | |
| Doris Ogilvie | Canada | Diving | 1932 Summer | |
| Flynn Ogilvie | Australia | Field hockey | 2020 Summer, 2024 Summer | |
| Oral Ogilvie | Canada | Athletics | 1992 Summer | |
| Peter Ogilvie | 1992 Summer, 1996 Summer | |
| Sarah Ann Ogilvie | Rowing | 1988 Summer | |
| Andrew Ogilvy-Wedderburn | Great Britain | Bobsleigh | 1976 Winter, 1980 Winter | |
| Masaji Ogino | Japan | Volleyball | 1992 Summer, 2008 Summer | |
| Hiroki Ogita | Athletics | 2016 Summer | |
| Chiharu Ogiwara | Boxing | 1984 Summer | |
| Kenji Ogiwara | Nordic combined | 1992 Winter, 1994 Winter, 1998 Winter, 2002 Winter | |
| Tsugiharu Ogiwara | 1998 Winter | |
| Valentina Ogiyenko | Soviet Union, Unified Team, Russia | Volleyball | 1988 Summer, 1992 Summer, 1996 Summer | |
| Sabahattin Oğlago | Turkey | Cross country skiing | 2002 Winter, 2006 Winter, 2010 Winter, 2014 Winter | |
| Diane Ogle | Australia | Luge | 1992 Winter | |
| Charlie Ogletree | United States | Sailing | 1996 Summer, 2000 Summer, 2004 Summer, 2008 Summer | |
| Dmitry Ogloblin | Soviet Union | Speed skating | 1980 Winter | |
| Ágúst Ögmundsson | Iceland | Handball | 1972 Summer | |
| Giuseppe Ogna | Italy | Track cycling | 1956 Summer | |
| Geminio Ognio | Water polo | 1948 Summer, 1952 Summer | |
| Tihomir Ognjanov | Yugoslavia | Football | 1952 Summer | |
| Maja Ognjenović | Serbia | Volleyball | 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Mirjana Ognjenović | Yugoslavia | Handball | 1980 Summer, 1984 Summer | |
| Amaka Ogoegbunam | Nigeria | Athletics | 2016 Summer | |
| Anthony Ogogo | Great Britain | Boxing | 2012 Summer | |
| Edith Ogoke | Nigeria | 2012 Summer | |
| Francis Ogola | Uganda | Athletics | 1992 Summer, 1996 Summer | |
| Mikhail Ogonkov | Soviet Union | Football | 1956 Summer | |
| Jerzy Ogórczyk | Poland | Ice hockey | 1964 Winter | |
| Denis O'Gorman | Great Britain | Athletics | 1960 Summer | |
| Aleksandr Ogorodnikov | Unified Team | Water polo | 1992 Summer | |
| Andrei Ogorodnikov | Kazakhstan | Ice hockey | 2006 Winter | |
| Oleg Ogorodov | Uzbekistan | Tennis | 1996 Summer | |
| Fortune Ogouchi | Benin | Athletics | 1988 Summer | |
| Jean Moloise Ogoudjobi | Taekwondo | 2008 Summer | |
| Stanislas Ogoudjobi | 2000 Summer | |
| Cathal O'Grady | Ireland | Boxing | 1996 Summer | |
| Dan O'Grady | Sailing | 1996 Summer | |
| Diane O'Grady | Canada | Rowing | 1996 Summer | |
| John O'Grady | Ireland | Athletics | 1924 Summer | |
| Kieren O'Grady | New Zealand | Field hockey | 1992 Summer | |
| Stuart O'Grady | Australia | Track cycling, Road cycling | 1992 Summer, 1996 Summer, 2000 Summer, 2004 Summer, 2008 Summer, 2012 Summer | |
| William O'Grady | Ireland | Football | 1948 Summer | |
| Ken Ograjenšek | Slovenia | Ice hockey | 2018 Winter | |
| Andreea Ogrăzeanu | Romania | Athletics | 2012 Summer | |
| Berkay Ömer Öğretir | Turkey | Swimming | 2020 Summer, 2024 Summer | |
| Nikola Ogrodníková | Czech Republic | Athletics | 2020 Summer, 2024 Summer | |
| Tatiana Ogrizko | Belarus | Rhythmic gymnastics | 1996 Summer | |
| Chamberlain Oguchi | Nigeria | Basketball | 2012 Summer, 2016 Summer | |
| Takahisa Oguchi | Japan | Luge | 2002 Winter, 2006 Winter, 2010 Winter | |
| Takako Oguchi | Skeleton | 2018 Winter | |
| Linda Ogugua | Nigeria | Basketball | 2004 Summer | |
| Charles Oguk | Kenya | Field hockey | 1988 Summer | |
| Gabriel Ogun | Nigeria | Boxing | 1968 Summer | |
| Naci Öğün | Turkey | Cross country skiing | 1968 Winter | |
| Abiola Ogunbanwo | Nigeria | Swimming | 2020 Summer | |
| Falilat Ogunkoya | Athletics | 1988 Summer, 1996 Summer, 2000 Summer | |
| Seun Ogunkoya | 1996 Summer, 2000 Summer | |
| Seye Ogunlewe | 2016 Summer | |
| Yemisi Ogunleye | Germany | 2024 Summer | |
| Femi Ogunode | Qatar | 2016 Summer, 2020 Summer | |
| Christianah Ogunsanya | Nigeria | Wrestling | 2024 Summer | |
| Kumiko Ogura | Japan | Badminton | 2008 Summer | |
| Shinji Ogura | Athletics | 1968 Summer | |
| Terumi Ogura | Road cycling | 1988 Summer | |
| Kazushige Oguri | Weightlifting | 1988 Summer | |
| Keiji Ogushi | Athletics | 1956 Summer, 1960 Summer, 1964 Summer | |
| Candeğer Kılınçer Oğuz | Turkey | 2004 Summer | |
| Fred Ogwang | Uganda | 1988 Summer | |
| Lawrence Ogwang | 1956 Summer | |
| Erica Ogwumike | Nigeria | Basketball | 2020 Summer | |
| Tensen Ogyu | Japan | Art competitions | 1932 Summer, 1936 Summer | |
| Oh Chwee Hock | Singapore | Water polo | 1956 Summer | |
| Oh Dae-keun | South Korea | Field hockey | 2012 Summer | |
| Oh Eun-seok | Fencing | 2004 Summer, 2008 Summer, 2012 Summer | |
| Oh Eun-su | Curling | 2018 Winter | |
| Frank Oh | Singapore | Shooting | 1976 Summer | |
| Oh Ha-na | South Korea | Fencing | 2012 Summer | |
| Oh Hye-ri | Taekwondo | 2016 Summer | |
| Oh Hyon-ho | Ice hockey | 2018 Winter | |
| Oh Jae-eun | Alpine skiing | 2006 Winter | |
| Oh Jae-il | Baseball | 2020 Summer | |
| Oh Jae-suk | Football | 2012 Summer | |
| Oh Jang-eun | 2008 Summer | |
| Oh Jea-han | Bobsleigh | 2014 Winter | |
| Oh Ji-hwan | Baseball | 2020 Summer | |
| Oh Jin-hyek | Archery | 2012 Summer, 2020 Summer | |
| Oh Ji-young | Volleyball | 2020 Summer | |
| Oh Joo-han | Athletics | 2020 Summer | |
| Oh Jung-yong | Wrestling | 1968 Summer | |
| Oh Kwang-soo | Boxing | 1988 Summer | |
| Oh Kyo-moon | Archery | 1996 Summer, 2000 Summer | |
| Oh Mi-ja | Athletics | 1996 Summer, 2000 Summer | |
| Oh Min-ji | Speed skating | 2010 Winter | |
| Oh Sang-eun | Table tennis | 2000 Summer, 2004 Summer, 2008 Summer, 2012 Summer | |
| Oh Sang-uk | Fencing | 2020 Summer, 2024 Summer | |
| Oh Seh-wong | Basketball | 1988 Summer | |
| Oh Se-jong | Short track speed skating | 2002 Winter, 2006 Winter | |
| Oh Seong-ok | Handball | 1992 Summer, 1996 Summer, 2000 Summer, 2004 Summer, 2008 Summer | |
| Seung-hwan Oh | Baseball | 2008 Summer, 2020 Summer | |
| Oh Seung-lip | Judo | 1972 Summer | |
| Oh Seung-shin | Field hockey | 1996 Summer, 2000 Summer | |
| Oh Seung-soon | Fencing | 1984 Summer | |
| Su-Hyun Oh | Australia | Golf | 2016 Summer | |
| Oh Sung-sik | South Korea | Basketball | 1996 Summer | |
| Oh Ye-jin | Shooting | 2024 Summer | |
| Oh Yeon-ji | Boxing | 2020 Summer, 2024 Summer | |
| Oh Yong-ran | Handball | 1996 Summer, 2000 Summer, 2004 Summer, 2008 Summer, 2016 Summer | |
| Oh Yong-seok | Speed skating | 1992 Winter | |
| Oh Young-ki | Handball | 1988 Summer | |
| Oh Yun-suk | 2004 Summer | |
| Ugo Oha | Nigeria | Basketball | 2004 Summer | |
| Dominique Ohaco | Chile | Freestyle skiing | 2014 Winter, 2018 Winter, 2022 Winter | |
| Edmundo Ohaco | Athletics | 1952 Summer | |
| Chinonye Ohadugha | Nigeria | 2008 Summer | |
| Hugh O'Hagan | Ireland | Boxing | 1948 Summer | |
| Osinachi Ohale | Nigeria | Football | 2024 Summer | |
| Frances O'Halloran | Canada | Athletics | 1952 Summer | |
| Kevin O'Halloran | Australia | Swimming | 1956 Summer | |
| Tom O'Halloran | Sport climbing | 2020 Summer | |
| Grace O'Hanlon | New Zealand | Field hockey | 2020 Summer | |
| Selena O'Hanlon | Canada | Equestrian eventing | 2008 Summer | |
| Patrick O'Hanrahan | Great Britain | Boxing | 1924 Summer | |
| Bill O'Hara | Ireland | Sailing | 1984 Summer, 1988 Summer | |
| John O'Hara | Australia | Wrestling | 1936 Summer | |
| Kelley O'Hara | United States | Football | 2012 Summer, 2016 Summer, 2020 Summer | |
| Michael O'Hara | Volleyball | 1964 Summer | |
| Tom O'Hara | Athletics | 1964 Summer | |
| Chris O'Hare | Great Britain | 2016 Summer | |
| Nicholas O'Hare | Ireland | Swimming | 1996 Summer | |
| Tommy O'Hare | United States | Short track speed skating | 1998 Winter | |
| Turlough O'Hare | Canada | Swimming | 1988 Summer, 1992 Summer | |
| Masaki Ohashi | Japan | Field hockey | 2020 Summer | |
| Masanori Ohashi | Wrestling | 1992 Summer | |
| Yui Ohashi | Swimming | 2020 Summer, 2024 Summer | |
| Ayumu Ōhata | Football | 2024 Summer | |
| Mariana Ohata | Brazil | Triathlon | 2000 Summer, 2004 Summer, 2008 Summer | |
| Masanobu Ohata | Japan | Shooting | 1976 Summer | |
| Takahiro Ohata | Handball | 1984 Summer | |
| Ayelet Ohayon | Israel | Fencing | 1996 Summer, 2000 Summer, 2004 Summer | |
| Henry Ohayon | Road cycling | 1960 Summer | |
| Jonathan Ohayon | Canada | Archery | 2004 Summer | |
| Jenna O'Hea | Australia | Basketball | 2012 Summer, 2020 Summer | |
| Fidan Ögel | Turkey | Judo | 2024 Summer | |
| Poul Ohff | Denmark | Sailing | 1952 Summer | |
| Hiroto Ohhara | Japan | Surfing | 2020 Summer | |
| Marie Ohier | France | Croquet | 1900 Summer | |
| Michael Ohioze | Great Britain | Athletics | 2020 Summer | |
| Mitsuhiro Ohira | Japan | Wrestling | 1956 Summer | |
| Reizo Ohira | Basketball | 1956 Summer | |
| Yoshihiro Ohira | Alpine skiing | 1964 Winter | |
| Christian Ohiri | Nigeria | Athletics | 1964 Summer | |
| Hiroaki Ohishi | Japan | Bobsleigh | 1998 Winter, 2002 Winter | |
| Mayumi Ohkutsu | Curling | 1998 Winter | |
| Volker Ohl | West Germany | Athletics | 1972 Summer | |
| Ulrich Öhlböck | Austria | Nordic combined, Cross country skiing | 1968 Winter, 1972 Winter | |
| Tim Ohlbrecht | Germany | Basketball | 2008 Summer | |
| Sig Ohlemann | Canada | Athletics | 1960 Summer | |
| Mattias Ohlin | Sweden | Swimming | 2000 Summer, 2004 Summer | |
| Sture Ohlin | Biathlon | 1964 Winter | |
| Victor Öhling Norberg | Freestyle skiing | 2014 Winter, 2018 Winter | |
| Jens Öhling | Ice hockey | 1984 Winter, 1988 Winter | |
| Eduard Ohlinger | West Germany | Weightlifting | 1988 Summer | |
| Henrik Ohlmeyer | Ski jumping | 1968 Winter | |
| Anders Ohlsén | Sweden | Canoe sprint | 1988 Summer, 1992 Summer | |
| Bertil Ohlson | Athletics | 1920 Summer | |
| Carl-Erik Ohlson | Sailing | 1952 Summer | |
| Olle Ohlson | Water polo | 1948 Summer | |
| Anna-Lisa Ohlsson | Canoe sprint | 1952 Summer | |
| Erik Ohlsson | Shooting | 1908 Summer, 1912 Summer, 1920 Summer | |
| Hjalmar Ohlsson | Athletics | 1912 Summer | |
| Olof Ohlsson | Football | 1908 Summer | |
| Patrik Ohlsson | Athletics | 1912 Summer | |
| Sven Ohlsson | Football | 1908 Summer | |
| Sven Ohlsson | Wrestling | 1912 Summer, 1920 Summer | |
| Thomas Ohlsson | Canoe sprint | 1980 Summer, 1984 Summer | |
| Mattias Öhlund | Ice hockey | 1998 Winter, 2002 Winter, 2006 Winter, 2010 Winter | |
| Fritz Ohlwärter | West Germany | Bobsleigh | 1976 Winter | |
| Jarl Öhman | Finland | Football | 1912 Summer | |
| Kenth Öhman | Sweden | Athletics | 1972 Summer | |
| Thomas Ohman | Australia | Canoe sprint | 1956 Summer | |
| Toivo Öhman | Sweden | Diving | 1952 Summer, 1960 Summer | |
| Anna Ohmiya | Japan | Curling | 2010 Winter | |
| Yoshiyuki Ohmiya | 1998 Winter | |
| Ivan Ohmut | Yugoslavia | Canoe sprint | 1972 Summer | |
| Apolo Ohno | United States | Short track speed skating | 2002 Winter, 2006 Winter, 2010 Winter | |
| Shinobu Ohno | Japan | Football | 2008 Summer, 2012 Summer | |
| Yukari Ohno | Ice hockey | 1998 Winter | |
| Aya Ohori | Badminton | 2024 Summer | |
| Takashi Ohori | Bobsleigh | 1994 Winter, 1998 Winter | |
| Martine Ohr | Netherlands | Field hockey | 1984 Summer, 1988 Summer, 1992 Summer | |
| Arvid Ohrling | Sweden | Athletics | 1912 Summer | |
| Uno Öhrlund | Ice hockey | 1964 Winter | |
| Emelie Öhrstig | Cross country skiing | 2006 Winter | |
| Isak Öhrström | Canoe slalom | 2016 Summer, 2024 Summer | |
| Akio Ohta | Japan | Speed skating | 2010 Winter | |
| Kunihiro Ohta | Equestrian jumping | 1956 Summer, 1960 Summer | |
| Riyu Ohta | Track cycling | 2024 Summer | |
| Tenyo Ohta | Art competitions | 1936 Summer | |
| Tomoki Ohta [ Wikidata ] | Athletics | 2024 Summer | |
| Atte Ohtamaa | Finland | Ice hockey | 2018 Winter, 2022 Winter | |
| Mei Ohtani | Japan | Rugby sevens | 2020 Summer, 2024 Summer | |
| Olli Ohtonen | Finland | Cross country skiing | 2006 Winter | |
| Toshio Ohtsu | Japan | Field hockey | 1936 Summer | |
| Tomeichi Ohura | Athletics | 1920 Summer | |
| Mariya Ohurtsova | Ukraine | Swimming | 2000 Summer | |
| Christine Ohuruogu | Great Britain | Athletics | 2004 Summer, 2008 Summer, 2012 Summer, 2016 Summer | |
| Victoria Ohuruogu | 2024 Summer | |
| Mana Ohyama | Japan | Handball | 2020 Summer | |
| Zevegiin Oidov | Mongolia | Wrestling | 1972 Summer, 1976 Summer, 1980 Summer | |
| Bjørg Løhner Øien | Norway | Figure skating | 1952 Winter | |
| Janek Õiglane | Estonia | Athletics | 2024 Summer | |
| Merijn van Oijen | Netherlands | Rowing | 2000 Summer | |
| Albert Öijermark | Sweden | Football | 1920 Summer | |
| Kalevi Oikarainen | Finland | Cross country skiing | 1968 Winter, 1972 Winter | |
| Toivo Oikarinen | 1952 Winter | |
| Azusa Oikawa | Japan | Fencing | 1984 Summer | |
| Fumihiro Oikawa | Figure skating | 1994 Winter | |
| Shihori Oikawa | Field hockey | 2020 Summer, 2024 Summer | |
| Yūya Oikawa | Speed skating | 2006 Winter, 2010 Winter, 2014 Winter | |
| Minato Oike | Cycling BMX freestyle | 2020 Summer | |
| Evangelos Oikonomakos | Greece | Boxing | 1968 Summer, 1972 Summer | |
| Aimilios Oikonomidis | Cyprus | Sailing | 2000 Summer | |
| Georgios Oikonomidis | Greece | Athletics | 2000 Summer | |
| Aikaterini Oikonomopoulou | Water polo | 2004 Summer, 2008 Summer | |
| Andrew Oikonomou | Athletics | 1904 Summer | |
| Nikos Oikonomou | Basketball | 1996 Summer | |
| Thanasis Oikonomou | Swimming | 2000 Summer | |
| Kazuyoshi Oimatsu | Japan | Figure skating | 1932 Winter, 1936 Winter | |
| Casper Oimoen | United States | Ski jumping | 1932 Winter, 1936 Winter | |
| Sumie Oinuma | Japan | Volleyball | 1968 Summer, 1972 Summer | |
| Maurizio Oioli | Italy | Skeleton | 2006 Winter, 2014 Winter | |
| Marit Øiseth | Norway | Cross country skiing | 1952 Winter | |
| Ayami Oishi | Japan | Rowing | 2016 Summer, 2020 Summer, 2024 Summer | |
| Yasuko Oishi | Swimming | 1952 Summer | |
| Koichi Oita | Football | 1936 Summer | |
| Chisaki Oiwa | Rhythmic gymnastics | 2020 Summer | |
| Yoshiaki Oiwa | Equestrian eventing | 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Johans Oja | Latvia | Athletics | 1924 Summer | |
| Kristjan Oja | Estonia | Biathlon | 1992 Winter | |
| Aleksi Ojala | Finland | Athletics | 2016 Summer, 2020 Summer | |
| Antero Ojala | Speed skating | 1936 Winter, 1948 Winter | |
| Teuvo Ojala | Wrestling | 1968 Summer | |
| Tuomo Ojala | Snowboarding | 2002 Winter | |
| Arvo Ojalehto | Weightlifting | 1980 Summer, 1984 Summer, 1988 Summer | |
| Niko Ojamäki | Ice hockey | 2022 Winter | |
| Janne Ojanen | 1988 Winter, 1994 Winter | |
| Jaakko Ojaniemi | Athletics | 2004 Summer | |
| Taina Ojaniemi | 1996 Summer, 2000 Summer, 2004 Summer | |
| Olavi Ojanperä | Canoe sprint | 1952 Summer, 1960 Summer | |
| Ilmar Ojase | Estonia | Swimming | 1992 Summer | |
| Kalju Ojaste | Biathlon | 1992 Winter, 1994 Winter, 1998 Winter | |
| Triin Ojaste | Cross country skiing | 2010 Winter, 2014 Winter | |
| Agustín Ojeda | Mexico | Football | 1928 Summer | |
| Andrea Ojeda | Argentina | 2008 Summer | |
| Augie Ojeda | United States | Baseball | 1996 Summer | |
| Edel Ojeda | Mexico | Boxing | 1948 Summer | |
| Enrique Ojeda | Chile | Shooting | 1936 Summer, 1952 Summer | |
| Eusebio Ojeda | Rowing | 1956 Summer | |
| Felipe Ojeda | Mexico | Canoe sprint | 1968 Summer, 1972 Summer | |
| Jaime Ojeda | Chile | Athletics | 1992 Summer | |
| José Leyver Ojeda | Mexico | 2012 Summer, 2016 Summer, 2020 Summer | |
| Roberto Ojeda | Cuba | Rowing | 1964 Summer, 1968 Summer, 1992 Summer | |
| Santiago Ojeda | Spain | Judo | 1972 Summer | |
| Sergio Ojeda | Chile | Boxing | 1928 Summer | |
| Jacob Ojee | Kenya | Rugby sevens | 2020 Summer | |
| Ifeanyi Emmanuel Ojeli | Nigeria | Athletics | 2020 Summer, 2024 Summer | |
| Rasmus Ojemaye | Boxing | 2000 Summer | |
| Pushpa Raj Ojha | Nepal | Athletics | 1984 Summer | |
| Amos Ojo | Nigeria | Wrestling | 1988 Summer, 1992 Summer | |
| Robert Ojo | Athletics | 1968 Summer, 1972 Summer | |
| Endurance Ojokolo | 2004 Summer | |
| Tade Ojora | Great Britain | 2024 Summer | |
| Samuel Ojserkis | United States | Rowing | 2016 Summer | |
| Chrisant Ojwang | Kenya | Rugby sevens | 2024 Summer | |
| Ok Duck-pil | South Korea | Sailing | 1996 Summer, 2000 Summer, 2004 Summer | |
| I Gusti Putu Oka Mona | Indonesia | Athletics | 1956 Summer | |
| Hideko Oka | Japan | Fencing | 1976 Summer | |
| Shinnosuke Oka | Artistic gymnastics | 2024 Summer | |
| Tomoko Oka | Fencing | 1984 Summer, 1988 Summer | |
| Zeynep Oka | Turkey | Shooting | 1988 Summer | |
| Michio Okabe | Japan | Field hockey | 1964 Summer | |
| Nagahira Okabe | Equestrian dressage | 1964 Summer | |
| Takanobu Okabe | Ski jumping | 1994 Winter, 1998 Winter, 2006 Winter | |
| Tetsuya Okabe | Alpine skiing | 1988 Winter, 1992 Winter, 1994 Winter | |
| Yukiaki Okabe | Swimming | 1964 Summer | |
| Tsutomu Okabori | Track cycling | 1976 Summer | |
| Hiroshi Okachi | Bobsleigh | 1984 Winter | |
| Harumitsu Okada | Track cycling | 1984 Summer | |
| Hirotaka Okada | Judo | 1988 Summer, 1992 Summer | |
| Keiju Okada | Sailing | 2020 Summer, 2024 Summer | |
| Kenneth Okada | United States | Judo | 1972 Summer | |
| Kozeki Okada | Japan | Equestrian dressage | 1928 Summer | |
| Kumiko Okada | Athletics | 2016 Summer, 2020 Summer, 2024 Summer | |
| Naoya Okada | Shooting | 2016 Summer, 2020 Summer, 2024 Summer | |
| Rana Okada | Snowboarding | 2010 Winter, 2014 Winter | |
| Shoken Okada | Canoe slalom | 1972 Summer | |
| Tony Okada | United States | Judo | 1992 Summer | |
| Emeka Okafor | Basketball | 2004 Summer | |
| Jahlil Okafor | Nigeria | 2020 Summer | |
| Rosemary Okafor | Athletics | 2000 Summer | |
| Blessing Okagbare | 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer | |
| Samuel Okai | Ghana | Football | 1964 Summer | |
| Toru Okajima | Japan | Ice hockey | 1968 Winter, 1972 Winter | |
| Zoltan Okalyi | Australia | Fencing | 1960 Summer | |
| Madoka Okamori [ Wikidata ] | Japan | Rhythmic gymnastics | 2000 Summer | |
| Daisuke Okamoto [ Wikidata ] | Handball | 2024 Summer | |
| Fuji Okamoto | Boxing | 1928 Summer | |
| Haruko Okamoto | Figure skating | 1968 Winter | |
| Hideo Okamoto | Rowing | 1972 Summer | |
| Keiko Okamoto | Canoe sprint | 1964 Summer | |
| Kumiko Okamoto | Tennis | 1988 Summer | |
| Mariko Okamoto | Volleyball | 1972 Summer, 1976 Summer | |
| Misugu Okamoto | Skateboarding | 2020 Summer | |
| Noboru Okamoto | Athletics | 1960 Summer, 1964 Summer | |
| Sunao Okamoto | Tennis | 1924 Summer | |
| Tadashi Okamoto | Boxing | 1968 Summer | |
| Tetsuo Okamoto | Brazil | Swimming | 1952 Summer | |
| Yoriko Okamoto | Japan | Taekwondo | 2000 Summer, 2004 Summer, 2008 Summer | |
| Yutaka Okamoto | Sailing | 1960 Summer | |
| Ikuko Okamura | Field hockey | 2008 Summer | |
| Mana Okamura | Artistic gymnastics | 2024 Summer | |
| Teruichi Okamura | 1972 Summer | |
| Tomio Okamura | Cross country skiing | 1972 Winter | |
| Eitaro Okano | Athletics | 1952 Summer | |
| Isao Okano | Judo | 1964 Summer | |
| Tomoyuki Okano | Rowing | 1988 Summer | |
| Michael Okantey | Ghana | Athletics | 1960 Summer, 1964 Summer | |
| Eva Okaro | Great Britain | Swimming | 2024 Summer | |
| Ibrahim Okash | Somalia | Athletics | 1984 Summer, 1988 Summer | |
| Ibrahim Okasha | Egypt | 1936 Summer | |
| Heizaburo Ōkawa | Japan | Fencing | 1960 Summer, 1964 Summer, 1968 Summer | |
| Keigo Okawa | Water polo | 2016 Summer, 2020 Summer, 2024 Summer | |
| Masumi Okawa | Artistic gymnastics | 1996 Summer | |
| Tadao Okayama | Cross country skiing | 1936 Winter | |
| Margaret Okayo | Kenya | Athletics | 2004 Summer | |
| Emiko Okazaki | Japan | Alpine skiing | 1972 Winter | |
| Haruka Okazaki | Canoe slalom | 2024 Summer | |
| Katsuo Okazaki | Athletics | 1924 Summer | |
| Naoto Okazaki | Fencing | 2000 Summer | |
| Satoko Okazaki | Artistic gymnastics | 1976 Summer | |
| Shinji Okazaki | Football | 2008 Summer | |
| Takayuki Okazaki | Athletics | 1960 Summer, 1964 Summer | |
| Tomomi Okazaki | Speed skating | 1994 Winter, 1998 Winter, 2002 Winter, 2006 Winter, 2010 Winter | |
| Akemi Okazato | Basketball | 1996 Summer | |
| Sewon Okazawa | Boxing | 2020 Summer, 2024 Summer | |
| Tosin Oke | Nigeria | Athletics | 2012 Summer, 2016 Summer | |
| Azubuike Okechukwu | Football | 2016 Summer | |
| Uche Okechukwu | 1996 Summer | |
| Lisa O'Keefe | Australia | Taekwondo | 2000 Summer | |
| Daniel O'Keeffe | Guam | Swimming | 2000 Summer, 2004 Summer | |
| Eileen O'Keeffe | Ireland | Athletics | 2008 Summer | |
| Fiona O'Keeffe | United States | 2024 Summer | |
| Michael O'Keeffe | New Zealand | Football | 2012 Summer | |
| Chidinma Okeke | Nigeria | 2024 Summer | |
| Jean Baptiste Okello | Uganda | Athletics | 1960 Summer | |
| Sylvanus Okello | Kenya | Boxing | 1984 Summer | |
| Brendan O'Kelly | Ireland | Football | 1948 Summer | |
| Con O'Kelly | Great Britain | Wrestling | 1908 Summer | |
| Cornelis O'Kelly | Boxing | 1924 Summer | |
| Janet Okelo | Kenya | Rugby sevens | 2016 Summer, 2020 Summer | |
| Micheline Okemba | Republic of the Congo | Handball | 1980 Summer | |
| Séraphine Okemba | France | Rugby sevens | 2020 Summer, 2024 Summer | |
| Kehinde Okenla | Nigeria | Table tennis | 2000 Summer | |
| Edith Oker | West Germany | Athletics | 1984 Summer | |
| Todd Okerlund | United States | Ice hockey | 1988 Winter | |
| Harald Økern | Norway | Nordic combined | 1924 Winter | |
| Olav Økern | Cross country skiing | 1948 Winter, 1952 Winter | |
| Fola Okesola | Great Britain | Boxing | 1996 Summer | |
| Chidi Okezie | Nigeria | Athletics | 2024 Summer | |
| Joe Okezie | Boxing | 1960 Summer | |
| Aleksandr Okhramenko | Kazakhstan | Weightlifting | 1996 Summer | |
| Miho Oki | Japan | Road cycling | 2000 Summer, 2004 Summer, 2008 Summer | |
| Seikan Oki | Athletics | 1932 Summer | |
| Makoto Okiguchi | Artistic gymnastics | 2008 Summer | |
| Yoshinori Okihara | Baseball | 2000 Summer | |
| Poliana Okimoto | Brazil | Marathon swimming | 2008 Summer, 2012 Summer, 2016 Summer | |
| Betty Okino | United States | Artistic gymnastics | 1992 Summer | |
| Oleksandr Okipniuk | Ukraine | Freestyle skiing | 2022 Winter | |
| Virgil Okiring | Uganda | Athletics | 1964 Summer | |
| Minoru Okita | Japan | Sailing | 1984 Summer | |
| Yoshio Okita | Athletics | 1928 Summer | |
| Harue Okitsu | Alpine skiing | 1972 Winter | |
| Simon Okker | Netherlands | Fencing | 1908 Summer | |
| Jong Ok-myong [ Wikidata ] | North Korea | Short track speed skating | 1998 Winter | |
| Seiji Oko | Japan | Volleyball | 1968 Summer, 1972 Summer, 1976 Summer | |
| Jay-Jay Okocha | Nigeria | Football | 1996 Summer | |
| Peter Okodogbe | Athletics | 1980 Summer | |
| Zhanyl Okoeva | Kyrgyzstan | Weightlifting | 2016 Summer | |
| Josh Okogie | Nigeria | Basketball | 2020 Summer | |
| Amelia Okoli | Athletics | 1964 Summer | |
| Emmanuel Okoli | 1992 Summer | |
| Lawrence Okolie | Great Britain | Boxing | 2016 Summer | |
| Courtney Okolo | United States | Athletics | 2016 Summer | |
| Vera Okolo | Nigeria | Football | 2004 Summer | |
| Effiong Okon | Boxing | 2004 Summer | |
| Paul Okon | Australia | Football | 1992 Summer | |
| Amy Okonkwo | Nigeria | Basketball | 2020 Summer, 2024 Summer | |
| Chibuzor Okonkwo | Football | 2008 Summer | |
| Christopher Okonkwo | Athletics | 1972 Summer | |
| Emilie O'Konor | Sweden | Ice hockey | 2006 Winter | |
| Reïna-Flor Okori | France | Athletics | 2004 Summer, 2008 Summer, 2012 Summer | |
| Chinwe Okoro | Nigeria | 2016 Summer | |
| Ifunanya Okoro | Basketball | 2024 Summer | |
| Marilyn Okoro | Great Britain | Athletics | 2008 Summer | |
| Lawrence Okoroafor | Nigeria | 1964 Summer | |
| Jerry Okorodudu | Boxing | 1984 Summer | |
| Georgii Okorokov | Australia | Wrestling | 2024 Summer | |
| Esther Okoronkwo | Nigeria | Football | 2024 Summer | |
| Isaac Okoronkwo | 2000 Summer | |
| Solomon Okoronkwo | 2008 Summer | |
| Nkiru Okosieme | 2000 Summer | |
| Mike Okot | Uganda | Athletics | 1984 Summer, 1988 Summer | |
| Petero Okotai | Cook Islands | Swimming | 2008 Summer | |
| John Okoth | Kenya | Rugby sevens | 2024 Summer | |
| John Eliud Okoth | Field hockey | 1988 Summer | |
| Nick Okoth | Boxing | 2008 Summer, 2020 Summer | |
| Collins Okothnyawallo | Weightlifting | 1996 Summer | |
| Rosvitha Okou | Ivory Coast | Athletics | 2012 Summer | |
| Viviane Okoula | Republic of the Congo | Handball | 1980 Summer | |
| Lawrence Okoye | Great Britain | Athletics | 2012 Summer, 2020 Summer, 2024 Summer | |
| Monica Okoye | Japan | Basketball | 2020 Summer | |
| KZ Okpala | Nigeria | 2020 Summer | |
| Sylvanus Okpala | Football | 1980 Summer, 1988 Summer | |
| Godwin Okpara | 2000 Summer | |
| Ezinne Okparaebo | Norway | Athletics | 2008 Summer, 2012 Summer, 2016 Summer | |
| Enekpedekumoh Okporu | Nigeria | Wrestling | 1992 Summer | |
| Maciej Okręglak | Poland | Canoe slalom | 2016 Summer | |
| Detlef Okrent | Germany | Field hockey | 1936 Summer | |
| Adam Okruashvili | Georgia | Judo | 2012 Summer, 2016 Summer | |
| Iwona Okrzesik | Poland | Archery | 1992 Summer | |
| Eino Oksanen | Finland | Athletics | 1956 Summer, 1960 Summer, 1964 Summer | |
| Hannu Oksanen | Ice hockey | 1984 Winter | |
| Jussi Oksanen | Snowboarding | 1998 Winter | |
| Lasse Oksanen | Ice hockey | 1964 Winter, 1968 Winter, 1972 Winter | |
| Julie Oksbjerg | Denmark | 2022 Winter | |
| Jan Økseter | Norway | Handball | 1972 Summer | |
| Józef Oksiutycz | Poland | Track cycling | 1928 Summer | |
| Mehmet Oktav | Turkey | Wrestling | 1948 Summer | |
| Melati Daeva Oktavianti | Indonesia | Badminton | 2020 Summer | |
| Zehra Öktem | Turkey | Archery | 1992 Summer | |
| Battulgyn Oktyabri | Mongolia | Short track speed skating | 1998 Winter, 2002 Winter | |
| Naoto Oku | Japan | Archery | 1992 Summer | |
| Toyoko Oku | 1988 Summer | |
| Séraphin Okuaka | Republic of the Congo | Judo | 1984 Summer | |
| Mehari Okubamicael [ Wikidata ] | Ethiopia | Road cycling | 1968 Summer, 1972 Summer | |
| Hideaki Okubo | Japan | Baseball | 1996 Summer | |
| Katsutoshi Okubo | Nordic combined | 1968 Winter | |
| Naotake Okubo | Rowing | 1960 Summer | |
| Takafumi Okubo | Sailing | 1964 Summer | |
| Yasuhiro Okubo | Wrestling | 1988 Summer | |
| Yoshito Ōkubo | Football | 2004 Summer | |
| Yuri Okubo | Snowboarding | 2018 Winter | |
| Shinji Okuda | Handball | 1988 Summer | |
| Yu Okudaira | Rugby sevens | 2024 Summer | |
| Nozomi Okuhara | Badminton | 2016 Summer, 2020 Summer | |
| Emil Okuliár | Czechoslovakia | Cross country skiing | 1956 Winter | |
| Wacław Okulicz-Kozaryn | Poland | Wrestling | 1924 Summer | |
| Judith Okumu | Kenya | Rugby sevens | 2020 Summer | |
| Peter Okumu | Uganda | Boxing | 1984 Summer | |
| Stephen Okumu | Kenya | 1984 Summer | |
| Mai Okumura | Japan | Volleyball | 2020 Summer | |
| Yoshihiro Okumura | Swimming | 2004 Summer, 2008 Summer | |
| Owen Okundaye | Nigeria | Athletics | 1960 Summer | |
| Fumiko Okuno | Japan | Artistic swimming | 1992 Summer | |
| Hiroaki Okuno | Volleyball | 1984 Summer | |
| Keisuke Okuno | Swimming | 1984 Summer | |
| Ryuzo Okuno | Equestrian jumping | 1988 Summer, 1992 Summer | |
| Samuel Okunowo | Nigeria | Football | 2000 Summer | |
| Oksana Okunyeva | Ukraine | Athletics | 2016 Summer | |
| Yume Okuroda | Japan | Rugby sevens | 2016 Summer | |
| Sotoo Okushiba | Cross country skiing | 1968 Winter | |
| Jean Marie Okutu | Spain | Athletics | 2016 Summer | |
| Keiji Okuyama | Japan | Wrestling | 1992 Summer | |
| Shozo Okuyama | Biathlon | 1968 Winter | |
| Zenji Okuzawa | Athletics | 1964 Summer | |
| Vivian Okwach | Kenya | Rugby sevens | 2020 Summer | |
| Samuel Okwaraji | Nigeria | Football | 1988 Summer | |
| Nwanneka Okwelogu | Athletics | 2016 Summer | |
| Rayton Okwiri | Kenya | Boxing | 2016 Summer | |
| Muhuttin Okyavuz | Turkey | Fencing | 1928 Summer | |
| Juan Olabarri | Spain | Sailing | 1964 Summer | |
| Leire Olaberria | Track cycling | 2008 Summer, 2012 Summer | |
| Adebayo Oladapo | Nigeria | Athletics | 1960 Summer | |
| Georgina Oladapo | Great Britain | 1996 Summer | |
| John Oladipo Oladitan | Nigeria | 1960 Summer | |
| Daniella Borda Olaechea [ Wikidata ] | Peru | Shooting | 2024 Summer | |
| Anna Ólafsdóttir | Iceland | Swimming | 1948 Summer | |
| Bryndís Ólafsdóttir | 1988 Summer | |
| Kolbrún Ólafsdóttir | 1948 Summer | |
| Frank Olafsen | Norway | Ice hockey | 1964 Winter | |
| Helene Olafsen | Snowboarding | 2010 Winter, 2014 Winter | |
| Einar Ólafsson | Iceland | Cross country skiing | 1984 Winter, 1988 Winter | |
| Jón Ólafsson | Athletics | 1964 Summer, 1968 Summer | |
| Magnús Ólafsson | Swimming | 1988 Summer | |
| Páll Ólafsson | Handball | 1988 Summer | |
| Shirley Gordon Olafsson | Canada | Athletics | 1948 Summer | |
| Sigurður Ólafsson | Iceland | Swimming | 1976 Summer | |
| Barbara Oláh | Hungary | Athletics | 2016 Summer, 2020 Summer | |
| Béla Oláh | Weightlifting | 1980 Summer, 1988 Summer | |
| Benedek Oláh | Finland | Table tennis | 2016 Summer | |
| Mihály Oláh | Hungary | Equestrian eventing | 1980 Summer | |
| Hakeem Olajuwon | United States | Basketball | 1996 Summer | |
| James Olakunle | Nigeria | Athletics | 1972 Summer | |
| Sule Olaleye | Table tennis | 1992 Summer, 1996 Summer | |
| Jesús Olalla | Spain | Handball | 1996 Summer, 2000 Summer | |
| Bibiana Olama | Equatorial Guinea | Athletics | 2012 Summer | |
| Olu Olamigoke | Nigeria | 2016 Summer | |
| Gösta Ölander | Sweden | Diving | 1936 Summer | |
| Mikael Olander | Athletics | 1988 Summer | |
| Rolf Olander | Swimming | 1952 Summer | |
| Philadelphia Olando | Kenya | Rugby sevens | 2016 Summer, 2020 Summer | |
| Abraham Olano | Spain | Road cycling | 1996 Summer, 2000 Summer | |
| Patricia Olano | Colombia | Swimming | 1968 Summer | |
| Olaitan Adam Olaore | Nigeria | Boxing | 2024 Summer | |
| Maria Olărașu | Moldova | Canoe sprint | 2020 Summer, 2024 Summer | |
| Ion Olărescu | Romania | Shooting | 1964 Summer, 1968 Summer | |
| Rafael Olarra | Chile | Football | 2000 Summer | |
| Costică Olaru | Romania | Canoe sprint | 1984 Summer | |
| Dan Olaru | Moldova | Archery | 2012 Summer, 2020 Summer, 2024 Summer | |
| Maria Olaru | Romania | Artistic gymnastics | 2000 Summer | |
| Nuța Olaru | Athletics | 2004 Summer | |
| Raluca Olaru | Tennis | 2016 Summer, 2020 Summer | |
| Ariel Olascoaga | Uruguay | Basketball | 1956 Summer | |
| Anna Olasz | Hungary | Marathon swimming | 2016 Summer, 2020 Summer | |
| Oyesade Olatoye | Nigeria | Athletics | 2024 Summer | |
| Fredrik Olausson | Sweden | Ice hockey | 2002 Winter | |
| Therese Olausson | Equestrian eventing | 1996 Summer | |
| Olav V | Norway | Sailing | 1928 Summer | |
| Riccardo Olavarrieta | Mexico | Figure skating | 1988 Winter, 1992 Winter | |
| Konráð Olavsson | Iceland | Handball | 1992 Summer | |
| Seidu Olawale | Nigeria | Wrestling | 1984 Summer | |
| María Olay | Spain | Swimming | 1996 Summer | |
| Andrea Olaya | Colombia | Wrestling | 2016 Summer | |
| Helen Olaye | Nigeria | Athletics | 1972 Summer | |
| Kenneth Olayombo | Football | 1968 Summer | |
| Gerd Olbert | West Germany | Water polo | 1972 Summer | |
| Bernd Olbricht | East Germany | Canoe sprint | 1976 Summer, 1980 Summer | |
| Kenan Olcay | Turkey | Wrestling | 1948 Summer | |
| Luis Alberto Olcese | Peru | Sailing | 2000 Summer | |
| Arek Olczak | Australia | Wrestling | 2000 Summer | |
| Eddie Olczyk | United States | Ice hockey | 1984 Winter | |
| Stanisław Olczyk | Poland | 1956 Winter, 1964 Winter | |
| Steven Old | New Zealand | Football | 2008 Summer | |
| Hans Oldag | United States | Athletics | 1932 Summer | |
| Stefan Ołdak | Poland | 1924 Summer | |
| Charles Oldaker | Great Britain | Artistic gymnastics | 1908 Summer | |
| Giuseppe Oldani | Italy | Boxing | 1924 Summer | |
| Richard Oldcorn | Great Britain | Fencing | 1964 Summer, 1968 Summer, 1972 Summer | |
| Sondre Olden | Norway | Ice hockey | 2014 Winter | |
| Keet Oldenbeuving | Netherlands | Skateboarding | 2020 Summer, 2024 Summer | |
| Marloes Oldenburg | Rowing | 2024 Summer | |
| Klaus Oldendorff | West Germany | Sailing | 1968 Summer | |
| Lisa Oldenhof | Australia | Canoe sprint | 2004 Summer, 2008 Summer | |
| Bert Oldershaw | Canada | 1948 Summer, 1952 Summer, 1956 Summer | |
| Dean Oldershaw | 1972 Summer, 1976 Summer | |
| Mark Oldershaw | 2008 Summer, 2012 Summer, 2016 Summer | |
| Reed Oldershaw | 1976 Summer | |
| Scott Oldershaw | 1984 Summer | |
| Brian Oldfield | United States | Athletics | 1972 Summer | |
| Clarence Oldfield | South Africa | 1920 Summer, 1924 Summer | |
| Pia-Sophie Oldhafer | Germany | Field hockey | 2016 Summer | |
| Megan Oldham | Canada | Freestyle skiing | 2022 Winter | |
| Sam Oldham | Great Britain | Artistic gymnastics | 2012 Summer | |
| Cian Oldknow [ Wikidata ] | South Africa | Athletics | 2024 Summer | |
| Albert Oldman | Great Britain | Boxing | 1908 Summer | |
| Barry Oldridge | New Zealand | Wrestling | 1976 Summer | |
| Jean Oldroyd | Great Britain | Swimming | 1960 Summer | |
| Shelley Olds | United States | Road cycling | 2012 Summer | |
| Wally Olds | Ice hockey | 1972 Winter | |
| Aisling O'Leary | Ireland | Swimming | 1972 Summer | |
| Bobby O'Leary | Athletics | 1992 Summer | |
| Connor O'Leary | Japan | Surfing | 2024 Summer | |
| John O'Leary | Great Britain | Shooting | 1924 Summer | |
| Meghan O'Leary | United States | Rowing | 2016 Summer, 2020 Summer | |
| Peter O'Leary | Ireland | Sailing | 2008 Summer, 2012 Summer | |
| Shaun O'Leary | New Zealand | Judo | 1984 Summer | |
| Artur Olech | Poland | Boxing | 1964 Summer, 1968 Summer | |
| Janusz Olech | Fencing | 1988 Summer, 1992 Summer, 1996 Summer | |
| Bogusława Olechnowicz | Judo | 1992 Summer | |
| Wiktor Olecki | Road cycling | 1936 Summer | |
| Léoncé Oleffe | Belgium | Athletics | 1920 Summer | |
| Ihor Olefirenko | Ukraine | 2016 Summer | |
| Olena Olefirenko | Rowing | 2004 Summer, 2008 Summer | |
| Sergiu Oleinic | Portugal | Judo | 2016 Summer | |
| Stanisław Olejniczak | Poland | Basketball | 1964 Summer | |
| Viktoriya Olekh | Ukraine | Cross country skiing | 2022 Winter | |
| Algis Oleknavicius | West Germany | Road cycling | 1972 Summer | |
| Štefan Olekšák | Czechoslovakia | Nordic combined | 1964 Winter | |
| Penny Oleksiak | Canada | Swimming | 2016 Summer, 2020 Summer, 2024 Summer | |
| David Oleme | Cameroon | Boxing | 1972 Summer | |
| Charles Olemus | Haiti | Athletics | 1976 Summer | |
| Kasey Olenberger | Italy | Baseball | 2004 Summer | |
| Juan Oleniak | Argentina | Football | 1960 Summer | |
| Adrian Olenici | Romania | Ice hockey | 1980 Winter | |
| Valentin Olenik | Soviet Union | Wrestling | 1964 Summer, 1968 Summer | |
| Valto Olenius | Finland | Athletics | 1948 Summer, 1952 Summer | |
| Mayobanex de Óleo | Dominican Republic | 2016 Summer | |
| Wesley Oler | United States | 1912 Summer | |
| Alf Olesen | Denmark | 1948 Summer | |
| Annelise Damm Olesen | 1968 Summer, 1972 Summer | |
| Claus Olesen | Sailing | 2004 Summer, 2012 Summer | |
| Gunner Olesen | Artistic gymnastics | 1948 Summer | |
| Nick Olesen | Ice hockey | 2022 Winter | |
| Robert Olesen | United States | Bobsleigh | 1998 Winter | |
| Thorbjørn Olesen | Denmark | Golf | 2016 Summer, 2024 Summer | |
| Jerzy Olesiak | Poland | Bobsleigh | 1956 Winter | |
| Jan Olesiński | Modern pentathlon | 1980 Summer | |
| Peeter Olesk | Estonia | Shooting | 2016 Summer, 2020 Summer, 2024 Summer | |
| Kurt Oleska | Germany | Basketball | 1936 Summer | |
| Rostislav Olesz | Czech Republic | Ice hockey | 2006 Winter | |
| Valentyn Oletsky | Ukraine | 2002 Winter | |
| Irena Olevsky | Australia | Artistic swimming | 2000 Summer | |
| Piotr Olewiński | Poland | Sailing | 1992 Summer | |
| Facundo Olezza | Argentina | 2016 Summer, 2020 Summer | |
| Mahdi Olfati | Iran | Artistic gymnastics | 2024 Summer | |
| Margrit Olfert | East Germany | Athletics | 1972 Summer | |
| Olha Rozshchupkina | Ukraine | Artistic gymnastics | 2000 Summer | |
| Ercole Olgeni | Italy | Rowing | 1920 Summer, 1924 Summer | |
| Gustavo Olguín [ Wikidata ] | Mexico | Water polo | 1952 Summer | |
| José Olguín | Chile | Football | 1928 Summer | |
| José Olguín | Mexico | Water polo | 1952 Summer | |
| Otilio Olguín | 1952 Summer | |
| Ercüment Olgundeniz | Turkey | Athletics | 2004 Summer, 2008 Summer, 2012 Summer | |
| Andrei Olhovskiy | Soviet Union, Russia | Tennis | 1988 Summer, 1996 Summer | |
| Ludwik Oli | Poland | Art competitions | 1928 Summer | |
| Samuel Oliech | Kenya | Rugby sevens | 2016 Summer | |
| Sam Olij | Netherlands | Boxing | 1928 Summer | |
| Staņislavs Olijars | Latvia | Athletics | 2000 Summer, 2004 Summer | |
| Andrejus Olijnikas | Lithuania | Canoe sprint | 2016 Summer, 2024 Summer | |
| Rune Olijnyk | Norway | Ski jumping | 1992 Winter | |
| Ruslan Olikhver | Unified Team, Russia | Volleyball | 1992 Summer, 1996 Summer, 2000 Summer | |
| Ken André Olimb | Norway | Ice hockey | 2014 Winter, 2018 Winter | |
| Mathis Olimb | 2010 Winter, 2014 Winter, 2018 Winter | |
| Johan Olin | Finland | Wrestling | 1912 Summer | |
| Ralf Olin | Canada | Speed skating | 1952 Winter, 1956 Winter, 1960 Winter, 1964 Winter | |
| Johnstone Olindi | Kenya | Rugby sevens | 2020 Summer | |
| Jean-Paul Olinger | Luxembourg | Fencing | 1960 Summer | |
| Rolf Olinger | Switzerland | Alpine skiing | 1948 Winter | |
| Ciarán Ó Lionáird | Ireland | Athletics | 2012 Summer | |
| Michael Olise | France | Football | 2024 Summer | |
| Azubuike Oliseh | Nigeria | 2000 Summer | |
| Sunday Oliseh | 1996 Summer | |
| Yuliya Olishevska | Ukraine | Athletics | 2016 Summer | |
| Grażyna Oliszewska | Poland | 1980 Summer | |
| Elvin Oliva | Honduras | Football | 2020 Summer | |
| Evaristo Oliva | Guatemala | Road cycling | 1968 Summer | |
| Georgina Oliva | Spain | Field hockey | 2008 Summer, 2016 Summer, 2020 Summer | |
| João Oliva | Brazil | Equestrian dressage | 2016 Summer, 2020 Summer, 2024 Summer | |
| Jordi Oliva | Spain | Field hockey | 1984 Summer, 1988 Summer | |
| Luis Oliva | Argentina | Athletics | 1932 Summer, 1936 Summer | |
| Patrizio Oliva | Italy | Boxing | 1980 Summer | |
| Roc Oliva | Spain | Field hockey | 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer | |
| Jesús Oliván | Athletics | 1992 Summer, 1996 Summer | |
| Daniel Olivares | Philippines | Road cycling | 1964 Summer | |
| Iván Olivares | Venezuela | Basketball | 1992 Summer | |
| Julián de Olivares | Spain | Fencing | 1924 Summer | |
| Rodrigo Olivares | Chile | Swimming | 2000 Summer | |
| Achille Olivari | Italy | Water polo | 1920 Summer | |
| Ivan Olivari | Croatia | Alpine skiing | 2006 Winter | |
| Andrés Olivas | Mexico | Athletics | 2020 Summer | |
| Nuria Olivé | Spain | Field hockey | 1992 Summer | |
| Abraham de Oliveira | Netherlands | Artistic gymnastics | 1908 Summer | |
| Alessandra Santos de Oliveira | Brazil | Basketball | 1996 Summer, 2000 Summer, 2004 Summer | |
| Amanda Oliveira | Water polo | 2016 Summer | |
| Anderson Oliveira | Canoe slalom | 2016 Summer | |
| Athos de Oliveira | Swimming | 1960 Summer, 1964 Summer | |
| Augusto Dutra de Oliveira | Athletics | 2016 Summer, 2020 Summer | |
| Benedicta de Oliveira | 1948 Summer | |
| Bernardo Oliveira | Archery | 2016 Summer | |
| Carlos Oliveira | Portugal | Rowing | 1972 Summer | |
| Carmem de Oliveira | Brazil | Athletics | 1992 Summer, 1996 Summer | |
| Celso Oliveira | Canoe sprint | 2016 Summer | |
| Edgar de Oliveira | Athletics | 1992 Summer, 1996 Summer | |
| Edith de Oliveira | Swimming | 1948 Summer, 1952 Summer | |
| Elisângela Oliveira | Volleyball | 2000 Summer, 2004 Summer | |
| Elói de Oliveira | 1976 Summer | |
| Ennio de Oliveira | Fencing | 1936 Summer | |
| Evandro Oliveira | Beach volleyball | 2016 Summer, 2020 Summer, 2024 Summer | |
| Fernanda Oliveira | Sailing | 2000 Summer, 2004 Summer, 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer | |
| Flávia Oliveira | Road cycling | 2016 Summer | |
| Geraldo de Oliveira | Athletics | 1948 Summer, 1952 Summer | |
| Gilda Oliveira | Wrestling | 2016 Summer | |
| Gisele de Oliveira | Athletics | 2008 Summer | |
| Gui Oliveira | Handball | 2008 Summer | |
| Gustavo Oliveira | Cycling BMX freestyle | 2024 Summer | |
| Hamilton de Oliveira | Volleyball | 1964 Summer | |
| Hélder Oliveira | Portugal | Athletics | 1988 Summer | |
| Ingrid Oliveira | Brazil | Diving | 2016 Summer, 2020 Summer, 2024 Summer | |
| Jeniffer Oliveira | Rhythmic gymnastics | 2004 Summer | |
| João Carlos de Oliveira | Athletics | 1976 Summer, 1980 Summer | |
| João Vítor de Oliveira | 2016 Summer | |
| Jorge de Oliveira | Shooting | 1952 Summer | |
| Júlio César de Oliveira | Athletics | 2016 Summer | |
| Larissa Oliveira | Swimming | 2016 Summer, 2020 Summer | |
| Lenice Oliveira | Volleyball | 1980 Summer | |
| Lorrane Oliveira | Artistic gymnastics | 2016 Summer, 2024 Summer | |
| Luiz Gabriel Oliveira | Boxing | 2024 Summer | |
| Manuel de Oliveira | Portugal | Athletics | 1960 Summer, 1964 Summer, 1968 Summer | |
| Márcio de Oliveira | Brazil | 1936 Summer | |
| Mauricio Oliveira | Sailing | 2000 Summer, 2004 Summer | |
| Nelson Oliveira | Portugal | Road cycling | 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Nicolas Oliveira | Brazil | Swimming | 2008 Summer, 2012 Summer, 2016 Summer | |
| Pâmella Oliveira | Triathlon | 2012 Summer, 2016 Summer | |
| Paulo André de Oliveira | Athletics | 2020 Summer, 2024 Summer | |
| Pedro Oliveira | Portugal | Swimming | 2008 Summer, 2012 Summer | |
| Pedro Luiz de Oliveira | Brazil | Athletics | 2016 Summer, 2020 Summer | |
| Raphael de Oliveira | 2000 Summer | |
| Roldeney de Oliveira [ Wikidata ] | São Tomé and Príncipe | Judo | 2024 Summer | |
| Ronilson Oliveira | Brazil | Canoe sprint | 2012 Summer | |
| Rui Oliveira | Portugal | Track cycling | 2024 Summer | |
| Ruy de Oliveira | Brazil | Swimming | 1972 Summer | |
| Sandra de Oliveira | Handball | 2000 Summer | |
| Sara Oliveira | Portugal | Swimming | 2008 Summer, 2012 Summer | |
| Sérgio Oliveira | Brazil | Judo | 1992 Summer | |
| Sérgio Oliveira | Portugal | Football | 2016 Summer | |
| Servílio de Oliveira | Brazil | Boxing | 1968 Summer | |
| Talmo Oliveira | Volleyball | 1992 Summer | |
| Tess Oliveira | Water polo | 2016 Summer | |
| Valéria de Oliveira | Handball | 2000 Summer | |
| Vitória Oliveira [ Wikidata ] | Portugal | Athletics | 2024 Summer | |
| Waldemar de Oliveira | Brazil | Boxing | 1972 Summer | |
| Walewska Oliveira | Volleyball | 2000 Summer, 2004 Summer, 2008 Summer | |
| Wanderley Oliveira | Boxing | 1988 Summer | |
| Amy Oliver | Great Britain | Archery | 2012 Summer | |
| Art Oliver | United States | Boxing | 1936 Summer | |
| Brian Oliver | Australia | Athletics | 1956 Summer | |
| Carl Oliver | Bahamas | 1996 Summer, 2000 Summer | |
| Célestin Oliver | France | Football | 1952 Summer | |
| Charlie Oliver | Solomon Islands | Athletics | 1984 Summer | |
| David Oliver | United States | 2008 Summer | |
| Don Oliver | New Zealand | Weightlifting | 1960 Summer, 1964 Summer, 1968 Summer | |
| George Oliver | United States | Golf | 1904 Summer | |
| Henry Oliver | Great Britain | Athletics | 1928 Summer | |
| Ilrey Oliver | Jamaica | 1984 Summer | |
| Jack Oliver | Great Britain | Weightlifting | 2012 Summer | |
| Jaime Oliver | Spain | Boxing | 1948 Summer | |
| Javianne Oliver | United States | Athletics | 2020 Summer | |
| John Oliver | Great Britain | Canoe sprint | 1968 Summer, 1972 Summer, 1976 Summer | |
| Jorge Oliver | Puerto Rico | Swimming | 2004 Summer | |
| Julio Oliver | Spain | Rowing | 1980 Summer, 1984 Summer | |
| Keith Oliver | Great Britain | Biathlon, Cross country skiing | 1972 Winter, 1976 Winter, 1980 Winter | |
| Lesley Oliver | Canoe sprint | 1968 Summer | |
| Lidoro Oliver | Argentina | Boxing | 1936 Summer | |
| Lucy Oliver | New Zealand | Athletics | 2012 Summer, 2016 Summer | |
| Luis Miguel Oliver | Spain | Rowing | 1980 Summer, 1984 Summer | |
| Mayan Oliver | Mexico | Modern pentathlon | 2020 Summer, 2024 Summer | |
| Percy Oliver | Australia | Swimming | 1936 Summer | |
| Reinaldo Oliver | Puerto Rico | Athletics | 1952 Summer, 1956 Summer | |
| Richard Oliver | Great Britain | Field hockey | 1968 Summer, 1972 Summer | |
| Robert Oliver | New Zealand | Road cycling | 1972 Summer | |
| True Oliver | Canada | Shooting | 1920 Summer | |
| Eduardo Olivera | Mexico | Modern pentathlon | 1968 Summer, 1972 Summer | |
| Érika Olivera | Chile | Athletics | 1996 Summer, 2000 Summer, 2004 Summer, 2012 Summer, 2016 Summer | |
| Héctor Olivera | Cuba | Baseball | 2008 Summer | |
| Lourdes Olivera | Mexico | Artistic swimming | 1992 Summer | |
| Luis Olivera | Cuba | Rowing | 1956 Summer | |
| Miguel Olivera | Athletics | 1968 Summer | |
| Marc Oliveras | Andorra | Alpine skiing | 2014 Winter, 2018 Winter | |
| Maximo Oliveras | Puerto Rico | Athletics | 1996 Summer | |
| Cora Olivero | Spain | 2004 Summer | |
| Gustavo Oliveros | Cuba | Fencing | 1968 Summer | |
| José Oliveros | Mexico | Athletics | 1968 Summer, 1972 Summer | |
| Princesa Oliveros | Colombia | 2012 Summer | |
| Åke Olivestedt | Sweden | Road cycling | 1948 Summer | |
| Olívia | Brazil | Basketball | 1996 Summer | |
| Abelardo Olivier | Italy | Fencing | 1908 Summer, 1920 Summer | |
| André Olivier | South Africa | Athletics | 2012 Summer | |
| Brigitte Olivier | Belgium | Judo | 2000 Summer | |
| Caroline Olivier | Canada | Freestyle skiing | 1994 Winter, 1998 Winter | |
| Esti Olivier [ Wikidata ] | South Africa | Canoe sprint | 2024 Summer | |
| Ethan Olivier | New Zealand | Athletics | 2024 Summer | |
| Eugène Olivier | France | Fencing | 1908 Summer | |
| Joseph Olivier | Rugby | 1900 Summer | |
| Marc-Antoine Olivier | Marathon swimming | 2016 Summer, 2020 Summer, 2024 Summer | |
| Roland Olivier | Switzerland | Field hockey | 1928 Summer | |
| Jorge Olivieri | Brazil | Basketball | 1956 Summer | |
| Juan Angel Olivieri | Argentina | Alpine skiing | 1976 Winter | |
| Linda Olivieri | Italy | Athletics | 2020 Summer | |
| Antonio Oliviero | Sailing | 1972 Summer | |
| Raúl Olivo | Venezuela | Shooting | 1956 Summer | |
| Jean-Marie Olivon | France | Water polo | 1992 Summer | |
| Elías Olivos [ Wikidata ] | Dominican Republic | Baseball | 1992 Summer | |
| Vyacheslav Oliynyk | Ukraine | Wrestling | 1996 Summer, 2000 Summer | |
| Anatoly Olizarenko | Soviet Union | Road cycling | 1964 Summer | |
| Nadezhda Olizarenko | Athletics | 1980 Summer, 1988 Summer | |
| Serhiy Olizarenko | 1980 Summer | |
| Belaynesh Oljira | Ethiopia | 2012 Summer | |
| Larisa Olkhina | Kazakhstan | Water polo | 2000 Summer | |
| Juho Olkinuora | Finland | Ice hockey | 2022 Winter | |
| Joonas Olkkonen | Shooting | 2004 Summer | |
| Sakari Olkkonen | Artistic gymnastics | 1960 Summer | |
| Vincent Olla | France | Canoe sprint | 1996 Summer | |
| Bo Ollander | Sweden | Speed skating | 1964 Winter | |
| Hely Ollarves | Venezuela | Athletics | 2000 Summer | |
| José Ollarves | Road cycling | 1976 Summer | |
| Alain Junior Ollé Ollé | Cameroon | Football | 2008 Summer | |
| Raul Olle | Estonia | Cross country skiing | 1998 Winter, 2002 Winter | |
| Keith Ollerenshaw | Australia | Athletics | 1956 Summer | |
| Scott Ollerenshaw | Football | 1988 Summer | |
| Harri Olli | Finland | Ski jumping | 2010 Winter | |
| Petra Olli | Wrestling | 2016 Summer | |
| Riitta Ollikka | Alpine skiing | 1976 Winter | |
| Antti Ollila | Freestyle skiing | 2014 Winter | |
| Patricia Ollinger | Mexico | Artistic gymnastics | 1972 Summer | |
| Ollivier [ Wikidata ] | France | 1900 Summer | |
| Pierre Ollivier | Belgium | Wrestling | 1924 Summer | |
| Corey Ollivierre | Grenada | Swimming | 2016 Summer | |
| Ewa Olliwier | Sweden | Diving | 1920 Summer, 1924 Summer | |
| Desiré Ollo | Gabon | Boxing | 1984 Summer | |
| Gustavo Ollo | Argentina | 1984 Summer | |
| Max d'Ollone | France | Art competitions | 1912 Summer | |
| Manuel Olmedo | Spain | Athletics | 2004 Summer, 2008 Summer | |
| Pablo Olmedo | Mexico | 2000 Summer | |
| Segundo Olmedo | Panama | Wrestling | 1972 Summer, 1976 Summer | |
| Monica Olmi | Italy | Swimming | 1984 Summer | |
| Angelica Olmo | Triathlon | 2020 Summer | |
| Antonio Olmo | Spain | Football | 1976 Summer | |
| Dani Olmo | 2020 Summer | |
| Giuseppe Olmo | Italy | Road cycling | 1932 Summer | |
| Giuliana Olmos | Mexico | Tennis | 2020 Summer | |
| Jesús Olmos | Basketball | 1936 Summer | |
| Juvenal Olmos | Chile | Football | 1984 Summer | |
| Conway Olmstead | United States | Sailing | 1928 Summer | |
| Barbara Olmsted | Canada | Canoe sprint | 1984 Summer, 1988 Summer | |
| Nancy Olmsted | 1988 Summer | |
| Alec Olney | Great Britain | Athletics | 1948 Summer | |
| Violet Olney | 1936 Summer | |
| Olatunji Olobia | Nigeria | 1988 Summer | |
| Anna Olofsson | Sweden | Snowboarding | 2006 Winter | |
| Fredrik Olofsson | Ice hockey | 2022 Winter | |
| Hans Olofsson | Alpine skiing | 1956 Winter | |
| Herbert Olofsson | Wrestling | 1936 Summer | |
| Johanna Olofsson | Ice hockey | 2014 Winter, 2018 Winter | |
| Karl-Uno Olofsson | Athletics | 1964 Summer | |
| Linda Olofsson | Swimming | 1992 Summer, 1996 Summer | |
| Martin Olofsson | Weightlifting | 1920 Summer, 1924 Summer | |
| Peter Olofsson | Handball | 1984 Summer | |
| Godwin Olofua | Nigeria | Badminton | 2020 Summer | |
| Saka Oloko | Athletics | 1960 Summer | |
| Ghyd-Kermeliss-Holly Olonghot | Republic of the Congo | 2008 Summer | |
| Obiageli Olorunsola [ Wikidata ] | Nigeria | Badminton | 1996 Summer | |
| Chris O'Loughlin | United States | Fencing | 1992 Summer | |
| David O'Loughlin | Ireland | Track cycling | 2008 Summer | |
| Gbenga Oloukun | Nigeria | Boxing | 2004 Summer | |
| Pius Olowo | Uganda | Athletics | 1980 Summer | |
| Karim Olowu | Nigeria | 1952 Summer, 1956 Summer | |
| Sanne van Olphen | Netherlands | Handball | 2016 Summer | |
| Louky van Olphen-van Amstel | Equestrian dressage | 1976 Summer | |
| Jean-Claude Olry | France | Canoe slalom | 1972 Summer | |
| Jean-Louis Olry | 1972 Summer | |
| Marte Olsbu Røiseland | Norway | Biathlon | 2018 Winter, 2022 Winter | |
| Agnete Olsen | Denmark | Swimming | 1924 Summer, 1928 Summer | |
| Alena Olsen | United States | Rugby sevens | 2024 Summer | |
| Alf Olsen | Denmark | Football | 1920 Summer | |
| Alf Olsen | Norway | Artistic gymnastics | 1952 Summer | |
| Anthon Olsen | Denmark | Football | 1912 Summer | |
| Anton Olsen | Norway | Shooting | 1920 Summer | |
| Arthur Olsen | Boxing | 1920 Summer | |
| Arthur Olsen | 1928 Summer | |
| Ben Olsen | United States | Football | 2000 Summer | |
| Björn Olsen | Iceland | Alpine skiing | 1968 Winter | |
| Carl Olsen | Norway | Road cycling | 1912 Summer | |
| Conrad Olsen | Rowing | 1920 Summer | |
| Einar Olsen | Denmark | Artistic gymnastics | 1912 Summer | |
| Eric Olsen | United States | Sailing | 1956 Summer | |
| Frithjof Olsen | Norway | Artistic gymnastics | 1908 Summer, 1912 Summer | |
| Georg Olsen | Denmark | Athletics | 1968 Summer | |
| Gerda Olsen | Swimming | 1952 Summer | |
| Gerhard Olsen | Norway | Athletics | 1912 Summer | |
| Godtfred Olsen | Denmark | Road cycling | 1912 Summer | |
| Grete Olsen | Fencing | 1932 Summer, 1936 Summer, 1948 Summer | |
| Håkon Olsen | Norway | Wrestling | 1952 Summer | |
| Halfdan Gran Olsen | Rowing | 1948 Summer | |
| Hanna Olsen | Sweden | Fencing | 1924 Summer, 1928 Summer | |
| Hans Olsen | Denmark | Road cycling | 1912 Summer | |
| Hans Olsen | Fencing | 1912 Summer | |
| Henry Olsen | Norway | Athletics | 1908 Summer | |
| Ib Olsen | Denmark | Rowing | 1948 Summer | |
| Inger Pors Olsen | 1988 Summer, 1996 Summer | |
| Jan-Erick Olsen | Norway | Swimming | 1984 Summer, 1988 Summer | |
| Joachim B. Olsen | Denmark | Athletics | 2000 Summer, 2004 Summer, 2008 Summer | |
| Jon Olsen | United States | Swimming | 1992 Summer, 1996 Summer | |
| Jonas Thor Olsen | Denmark | Cross country skiing | 2010 Winter | |
| Justin Olsen | United States | Bobsleigh | 2010 Winter, 2014 Winter, 2018 Winter | |
| Kate Olsen | Denmark | Canoe sprint | 1972 Summer, 1976 Summer | |
| Katrin Olsen | Rowing | 2008 Summer | |
| Knud Olsen | 1928 Summer, 1936 Summer | |
| Knut K. Olsen [ Wikidata ] | Norway | Swimming | 1928 Summer | |
| Kristoffer Olsen | Sailing | 1920 Summer | |
| Lars Olsen | Denmark | Track cycling | 1988 Summer | |
| Lotte Olsen | Badminton | 1996 Summer | |
| Lærke Olsen | Judo | 2020 Summer, 2024 Summer | |
| Madison Olsen | United States | Freestyle skiing | 2018 Winter | |
| Marcos José Olsen | Brazil | Shooting | 1972 Summer, 1976 Summer, 1980 Summer, 1984 Summer | |
| Marie Thusgaard Olsen | Denmark | Sailing | 2020 Summer | |
| Martin Olsen | Boxing | 1920 Summer | |
| Mats Rosseli Olsen | Norway | Ice hockey | 2014 Winter, 2018 Winter | |
| May Irene Olsen | Shooting | 1988 Summer | |
| Morten Olsen | Denmark | Handball | 2016 Summer, 2020 Summer | |
| Niels Olsen | Rowing | 1964 Summer | |
| Ole Olsen | Shooting | 1908 Summer, 1912 Summer | |
| Oliver Olsen [ Wikidata ] | United States | Artistic gymnastics | 1904 Summer | |
| Orla Olsen | Denmark | Athletics | 1928 Summer | |
| Oskar Olsen | Norway | Speed skating | 1924 Winter, 1928 Winter | |
| Otto Olsen | Shooting | 1920 Summer, 1924 Summer | |
| Otto Olsen | Denmark | Modern pentathlon | 1924 Summer, 1928 Summer | |
| Øystein Olsen | Norway | Ice hockey | 1992 Winter | |
| Per Olsen | Swimming | 1952 Summer | |
| Per Olsen | Cross country skiing | 1956 Winter | |
| Per Erling Olsen | Athletics | 1984 Summer | |
| Per Olaf Olsen [ Wikidata ] | Shooting | 1908 Summer | |
| Per Skjerwen Olsen | Ice hockey | 1964 Winter, 1968 Winter | |
| Richard Olsen | Denmark | Rowing | 1936 Summer | |
| Phil Olsen | Canada | Athletics | 1976 Summer | |
| Poppy Starr Olsen | Australia | Skateboarding | 2020 Summer | |
| Ragnar Olsen | Norway | Athletics | 1952 Summer | |
| Ragnvald Olsen | Wrestling | 1924 Summer | |
| Reno Olsen | Denmark | Track cycling | 1968 Summer, 1972 Summer | |
| Rigmor Olsen | Swimming | 1928 Summer | |
| Rikke Olsen | Badminton | 1996 Summer, 2000 Summer, 2004 Summer | |
| Rolf Olsen | Norway | Canoe sprint | 1960 Summer, 1968 Summer | |
| Shallon Olsen | Canada | Artistic gymnastics | 2016 Summer, 2020 Summer, 2024 Summer | |
| Steen Olsen | Denmark | 1912 Summer, 1920 Summer | |
| Steffen Olsen | Shooting | 2020 Summer | |
| Svend Olsen | Weightlifting | 1932 Summer | |
| Thor Olsen | Norway | 1952 Summer | |
| Thor Egil Olsen | Rowing | 1972 Summer | |
| Thorleif Olsen | Football | 1952 Summer | |
| Thorvald Olsen | Wrestling | 1912 Summer | |
| Torben Ulsø Olsen | Denmark | Equestrian dressage | 1984 Summer | |
| Viktor Olsen | Norway | Athletics | 1952 Summer | |
| Wilhelm Olsen | Wrestling | 1920 Summer | |
| Willy Olsen | Speed skating | 1972 Winter | |
| Zoe Ann Olsen-Jensen | United States | Diving | 1948 Summer, 1952 Summer | |
| Igor Olshanetskyi | Israel | Weightlifting | 2016 Summer | |
| Volodymyr Olshanskiy | Ukraine | Cross country skiing | 2006 Winter | |
| Sergei Olshansky | Soviet Union | Football | 1972 Summer | |
| Yevgeniya Olshevskaya | Russia | Diving | 2000 Summer | |
| Aaron Olson | New Zealand | Basketball | 2004 Summer | |
| Billy Olson | United States | Athletics | 1988 Summer | |
| Brian Olson | Judo | 1996 Summer, 2000 Summer, 2004 Summer, 2008 Summer | |
| Diana Olson | Rowing | 1992 Summer | |
| Eivor Olson | Sweden | Athletics | 1948 Summer, 1952 Summer | |
| Evan Olson | United States | Rowing | 2024 Summer | |
| Gösta Olson | Sweden | Fencing, Artistic gymnastics | 1908 Summer | |
| Jeff Olson | United States | Alpine skiing | 1988 Winter, 1992 Winter | |
| Oscar Olson | Tug of war, Weightlifting | 1904 Summer | |
| Patty Olson | Canada | Volleyball | 1976 Summer | |
| Ragnar Olson | Sweden | Equestrian dressage | 1928 Summer | |
| Sasha Olson | Canada | Softball | 2004 Summer | |
| Scotty Olson | Boxing | 1988 Summer | |
| Weldon Olson | United States | Ice hockey | 1956 Winter, 1960 Winter | |
| Willis S. Olson | Ski jumping | 1952 Winter, 1956 Winter | |
| Gyda Ellefsplass Olssen | Norway | Shooting | 2008 Summer | |
| Albert Olsson | Sweden | Football | 1920 Summer | |
| Anna Olsson | Canoe sprint | 1984 Summer, 1988 Summer, 1992 Summer, 1996 Summer, 2000 Summer | |
| Anna Olsson | Cross country skiing | 2002 Winter, 2006 Winter, 2010 Winter | |
| Anneli Olsson | Athletics | 1972 Summer | |
| Arthur Olsson | Cross country skiing | 1956 Winter | |
| August Olsson | Sailing | 1908 Summer | |
| Robert Olsson | Athletics | 1908 Summer, 1912 Summer, 1920 Summer | |
| Christian Olsson | 2000 Summer, 2004 Summer | |
| Diana Olsson | Swimming | 1972 Summer, 1976 Summer | |
| Ejnar Olsson | Ice hockey | 1924 Winter | |
| Erik Olsson | Wrestling | 1964 Summer | |
| Eva Olsson | Cross country skiing | 1972 Winter, 1976 Winter, 1980 Winter | |
| Frank Olsson | Rowing | 1952 Summer | |
| Glenn Olsson | Biathlon | 1994 Winter | |
| Gunhild Olsson | Athletics | 1972 Summer | |
| Gunnar Olsson | Canoe sprint | 1988 Summer, 1992 Summer | |
| Hanna Olsson | Ice hockey | 2018 Winter | |
| Hans Olsson | Canoe sprint | 1988 Summer, 1992 Summer | |
| Hans Olsson | Alpine skiing | 2010 Winter | |
| Holmfrid Olsson | Biathlon | 1968 Winter, 1972 Winter | |
| Jenny Olsson | Cross country skiing | 2002 Winter | |
| Jens Olsson | Badminton | 1992 Summer, 1996 Summer | |
| Johan Olsson | Cross country skiing | 2006 Winter, 2010 Winter, 2014 Winter | |
| Jörgen Olsson | Wrestling | 1992 Summer | |
| Josefin Olsson | Sailing | 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Karin Olsson | Canoe sprint | 1980 Summer | |
| Karin Margareta Olsson | Bobsleigh | 2002 Winter | |
| Lars Olsson | Cross country skiing | 1960 Winter, 1964 Winter | |
| Lars Olsson | Alpine skiing | 1964 Winter, 1968 Winter | |
| Liselotte Olsson | Canoe sprint | 1988 Summer | |
| Mats Olsson | Handball | 1984 Summer, 1988 Summer, 1992 Summer, 1996 Summer | |
| Matts Olsson | Alpine skiing | 2014 Winter, 2018 Winter | |
| Nils Olsson | Art competitions | 1948 Summer | |
| Olle Olsson | Handball | 1972 Summer | |
| Oluf Olsson | Denmark | Artistic gymnastics | 1908 Summer, 1912 Summer | |
| Per-Olof Olsson | Sweden | Swimming | 1948 Summer | |
| Roger Olsson | Ice hockey | 1968 Winter | |
| Salina Olsson | Football | 2004 Summer | |
| Sean Olsson | Great Britain | Bobsleigh | 1994 Winter, 1998 Winter | |
| Staffan Olsson | Sweden | Handball | 1988 Summer, 1992 Summer, 1996 Summer, 2000 Summer | |
| Sten Olsson | 1972 Summer | |
| Svante Olsson | Athletics | 1912 Summer | |
| Sven Olsson | Football | 1908 Summer | |
| Thorild Olsson | Athletics | 1912 Summer | |
| Abraham van Olst | Netherlands | Water polo | 1928 Summer | |
| Anne van Olst | Denmark | Equestrian dressage | 1988 Summer, 1992 Summer, 2000 Summer, 2008 Summer, 2012 Summer | |
| Frithjof Olstad | Norway | Rowing | 1912 Summer | |
| Oscar Olstad | Artistic gymnastics | 1912 Summer | |
| Nico Olsthoorn | Netherlands | Speed skating | 1956 Winter | |
| Aleksandra Olsza | Poland | Tennis | 1996 Summer | |
| Alfons Olszewski | Sailing | 1936 Summer | |
| Leszek Olszewski | Boxing | 1992 Summer | |
| Pawel Olszewski | Germany | Modern pentathlon | 1992 Summer | |
| Piotr Olszewski | Poland | Rowing | 1996 Summer | |
| Ryszard Olszewski | Basketball | 1960 Summer | |
| Włodzimierz Olszewski | Ice hockey | 1984 Winter | |
| Csongor Olteán | Hungary | Athletics | 2008 Summer | |
| Daniela Oltean | Romania | Speed skating | 2002 Winter, 2006 Winter | |
| Sebastian Oltean [ Wikidata ] | Water polo | 2024 Summer | |
| Florian Olteanu | Bobsleigh | 1988 Winter | |
| George Olteanu | Boxing | 1996 Summer, 2000 Summer | |
| Gheorghe Olteanu | Cross country skiing | 1952 Winter | |
| Ioana Olteanu | Rowing | 1992 Summer, 1996 Summer, 2000 Summer | |
| Iulia Olteanu | Athletics | 1996 Summer | |
| Ovidiu Olteanu | 1996 Summer | |
| Stela Olteanu | 1996 Summer | |
| Jutta Oltersdorf | West Germany | Artistic gymnastics | 1972 Summer, 1976 Summer | |
| Bekmurod Oltiboev | Uzbekistan | Judo | 2020 Summer | |
| Toby Olubi | Great Britain | Bobsleigh | 2018 Winter | |
| Adewale Olukoju | Nigeria | Athletics | 1988 Summer, 1996 Summer | |
| John Olulu | Kenya | Boxing | 1964 Summer, 1968 Summer | |
| Segun Olumodeji | Nigeria | Football | 1968 Summer | |
| Jeff Oluoch | Kenya | Rugby sevens | 2020 Summer | |
| Veronica Oluoch | Volleyball | 2024 Summer | |
| Batholomew Oluoma | Nigeria | Weightlifting | 1984 Summer | |
| Ajose Olusegun | Boxing | 2000 Summer | |
| Mojisola Oluwa | Weightlifting | 1996 Summer | |
| Rafiu Oluwa | Athletics | 1952 Summer, 1956 Summer | |
| Peter Ölvecký | Slovakia | Ice hockey | 2014 Winter, 2018 Winter | |
| Heather Olver | Great Britain | Badminton | 2016 Summer | |
| Jeff Olver | Australia | Football | 1988 Summer | |
| Alfredo Olvera | Mexico | Wrestling | 1972 Summer, 1980 Summer | |
| Aline Olvera | Rowing | 2004 Summer | |
| Bernardo Olvera | Wrestling | 1984 Summer, 1988 Summer | |
| Jorge Olvera | 1988 Summer | |
| Osmar Olvera | Diving | 2020 Summer, 2024 Summer | |
| Andres Olvik | Estonia | Swimming | 2008 Summer | |
| Sunday Olweny | Uganda | Athletics | 1988 Summer | |
| Lyudmyla Olyanovska | Ukraine | 2020 Summer, 2024 Summer | |
| 1928 Summer Olympics | Switzerland | Art competitions | 1928 Summer | |
| Chant Olympique [ Wikidata ] | France | 1928 Summer | |
| Brent Olynyk | Canada | Badminton | 2000 Summer | |
| Kelly Olynyk | Basketball | 2024 Summer | |
| Marjan Olyslager | Netherlands | Athletics | 1988 Summer | |
| Nicola Olyslagers | Australia | 2020 Summer, 2024 Summer | |
| Nikolay Olyunin | Russia, Russian Olympic Committee | Snowboarding | 2014 Winter, 2018 Winter | |
| Alevtina Olyunina | Soviet Union | Cross country skiing | 1968 Winter, 1972 Winter | |
| Tserenjavyn Ölziibayar | Mongolia | Shooting | 1972 Summer, 1976 Summer | |
| Jamsrangiin Ölzii-Orshikh | Road cycling | 1992 Summer | |
| Dashnyamyn Olzvoi | Boxing | 1976 Summer | |
| Om Jong-guk | North Korea | Weightlifting | 1976 Summer | |
| Om Jong-ran | Football | 2008 Summer | |
| Om Yun-chol | Weightlifting | 2012 Summer, 2016 Summer | |
| Majemite Omagbaluwaje | Nigeria | Judo | 1988 Summer, 1992 Summer, 2000 Summer | |
| Florence Omagbemi | Football | 2000 Summer | |
| Jimmy Omagbemi | Athletics | 1960 Summer, 1964 Summer | |
| Gerard O'Mahony | Australia | Boxing | 2004 Summer, 2008 Summer | |
| Khalifa Bin Omair [ Wikidata ] | United Arab Emirates | Road cycling | 1988 Summer, 1992 Summer | |
| Lubna Al-Omair | Saudi Arabia | Fencing | 2016 Summer | |
| Eugene Omalla | Netherlands | Athletics | 2024 Summer | |
| Kieran O'Malley | Great Britain | Volleyball | 2012 Summer | |
| Terry O'Malley | Canada | Ice hockey | 1964 Winter, 1968 Winter, 1980 Winter | |
| Miro Oman | Yugoslavia | Ski jumping | 1964 Winter | |
| Paul Sewe Omany | Kenya | Field hockey | 1988 Summer | |
| Abdul Omar | Ghana | Boxing | 2016 Summer | |
| Abdul Rahman Omar | Kenya | Shooting | 1972 Summer | |
| Ahmed Omar | Morocco | Road cycling | 1960 Summer | |
| Ali Omar | Libya | Judo | 2020 Summer | |
| Bashar Omar | Kuwait | Athletics | 2004 Summer | |
| Samia Yusuf Omar | Somalia | 2008 Summer | |
| Yahia Omar | Egypt | Handball | 2020 Summer, 2024 Summer | |
| Youssef Ali Omar | Athletics | 1952 Summer | |
| Frank O'Mara | Ireland | 1984 Summer, 1988 Summer, 1992 Summer | |
| Linus Omark | Sweden | Ice hockey | 2018 Winter | |
| Artur Omarov | Czech Republic | Wrestling | 2020 Summer | |
| Magomed Omarov | Russia | Boxing | 2012 Summer | |
| Anna Omarova | Athletics | 2008 Summer | |
| Kano Omata | Japan | Artistic swimming | 2016 Summer | |
| Paul Omba-Biongolo | France | Boxing | 2016 Summer | |
| Dennis Ombachi | Kenya | Rugby sevens | 2016 Summer | |
| François Ombanzi | Democratic Republic of the Congo | Road cycling | 1968 Summer | |
| Orlann Oliere | France | Athletics | 2020 Summer, 2024 Summer | |
| Nelson Ombito | Kenya | Judo | 1988 Summer | |
| Ryan O'Meara | United States | Figure skating | 2006 Winter | |
| Juan Omedes | Spain | Rowing | 1948 Summer, 1952 Summer | |
| Luis Omedes | 1924 Summer | |
| Luis Omedes | Rowing, Luge | 1952 Summer, 1968 Winter | |
| Igor Omelchenko | Soviet Union | Swimming | 1976 Summer | |
| Sergey Omelchenko | Nordic combined | 1980 Winter | |
| Oleh Omelchuk | Ukraine | Shooting | 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer | |
| Jeanne Omelenchuk | United States | Speed skating | 1960 Winter, 1968 Winter, 1972 Winter | |
| Mariya Omelianovych | Soviet Union | Rowing | 1988 Summer | |
| Igor Omelin | Russian Olympic Committee | Freestyle skiing | 2018 Winter, 2022 Winter | |
| Rafał Omelko | Poland | Athletics | 2016 Summer | |
| Viktor Omelyanovich | Soviet Union | Rowing | 1988 Summer | |
| Akuoma Omeoga | Nigeria | Bobsleigh | 2018 Winter | |
| Thierry Omeyer | France | Handball | 2004 Summer, 2008 Summer, 2012 Summer, 2016 Summer | |
| Jarl Omholt-Jensen | Canada | Cross country skiing | 1972 Winter | |
| Ireneusz Omięcki | Poland | Rowing | 1988 Summer | |
| Navina Omilade | Germany | Football | 2004 Summer | |
| Steve Omischl | Canada | Freestyle skiing | 2002 Winter, 2006 Winter, 2010 Winter | |
| Masashi Omiya | Japan | Road cycling | 1960 Summer, 1964 Summer | |
| Wim Omloop | Belgium | 1992 Summer | |
| Manfred Ommer | West Germany | Athletics | 1972 Summer | |
| Harcourt Ommundsen | Great Britain | Shooting | 1908 Summer, 1912 Summer | |
| Gilbert Omnès | France | Athletics | 1948 Summer | |
| Philippe Omnès | Fencing | 1984 Summer, 1988 Summer, 1992 Summer, 1996 Summer | |
| Sylvester Omodiale | Nigeria | Athletics | 2000 Summer | |
| Bright Omokaro | Football | 1988 Summer | |
| Amos Omolo | Uganda | Athletics | 1964 Summer, 1968 Summer | |
| Kasmiro Omona | Boxing | 1988 Summer | |
| James Omondi | Kenya | 1984 Summer | |
| Michael Omondi | Field hockey | 1984 Summer, 1988 Summer | |
| Sinaida Omondi | Rugby sevens | 2020 Summer | |
| Elizabeth Omoregie | Slovenia | Handball | 2024 Summer | |
| Shigekazu Ōmori | Japan | Athletics | 1996 Summer | |
| Shigenori Omori | 1984 Summer | |
| Janet Omorogbe | Nigeria | 1968 Summer | |
| Loveth Omoruyi | Italy | Volleyball | 2024 Summer | |
| Roland Omoruyi | Nigeria | Boxing | 1980 Summer, 1984 Summer | |
| Nuni Omot | South Sudan | Basketball | 2024 Summer | |
| Titus Omotara | Nigeria | Table tennis | 1988 Summer | |
| Olajide Omotayo | 2020 Summer, 2024 Summer | |
| Hideki Omoto | Japan | Rowing | 2016 Summer | |
| Rika Omoto | Swimming | 2020 Summer | |
| Sakurako Omoto | Field hockey | 2020 Summer, 2024 Summer | |
| Omolara Ogunmakinju | Nigeria | Athletics | 2012 Summer, 2016 Summer | |
| Naser Al-Omran | Kuwait | Football | 2000 Summer | |
| Nasser Al-Omran | Saudi Arabia | 2020 Summer | |
| Mohamed Omrani | Tunisia | Taekwondo | 2004 Summer | |
| Nataliya Omsheva | Soviet Union | Luge | 1972 Winter | |
| Ragnar Omtvedt | United States | Cross country skiing, Nordic combined | 1924 Winter | |
| Asumi Ōmura | Japan | Canoe sprint | 2012 Summer | |
| Kanako Omura | Volleyball | 2004 Summer, 2008 Summer | |
| Waichiro Omura | Football | 1956 Summer | |
| Ferdinand Omanyala | Kenya | Athletics | 2020 Summer, 2024 Summer | |
| Curt Onalfo | United States | Football | 1992 Summer | |
| Nelson Onana | Belgium | Field hockey | 2024 Summer | |
| Jennifer Onasanya [ Wikidata ] | Austria | Bobsleigh | 2022 Winter | |
| Givi Onashvili | Soviet Union | Judo | 1972 Summer | |
| Nelson Oñate | Cuba | Shooting | 1968 Summer | |
| Kōshirō Onchi | Japan | Art competitions | 1932 Summer | |
| Chawalit On-Chim | Thailand | Boxing | 1972 Summer | |
| Donald Onchiri | Kenya | Athletics | 1996 Summer | |
| Noelia Oncina | Spain | Handball | 2004 Summer | |
| Jaime Oncins | Brazil | Tennis | 1992 Summer, 2000 Summer | |
| Eyüp Öncü | Turkey | Equestrian jumping | 1948 Summer | |
| Masashi Onda | Japan | Field hockey | 1968 Summer | |
| Yoshie Onda | Figure skating | 2002 Winter | |
| Yuichi Onda | Cross country skiing | 2006 Winter, 2010 Winter, 2014 Winter | |
| Christopher Ondaatje | Canada | Bobsleigh | 1964 Winter | |
| Ahmet Önder | Turkey | Artistic gymnastics | 2020 Summer, 2024 Summer | |
| Kennedy Ondiek | Kenya | Athletics | 1988 Summer, 1992 Summer | |
| Yobes Ondieki | 1988 Summer, 1992 Summer | |
| Chiara Ondoli | Italy | Rowing | 2020 Summer | |
| Oriane Ondono | France | Handball | 2024 Summer | |
| Adam Ondra | Czech Republic | Sport climbing | 2020 Summer, 2024 Summer | |
| Ladislav Ondřej | Czechoslovakia | Shooting | 1952 Summer | |
| Marcos Ondruska | South Africa | Tennis | 1996 Summer | |
| Lacey O'Neal | United States | Athletics | 1964 Summer, 1972 Summer | |
| Shaquille O'Neal | Basketball | 1996 Summer | |
| Denis O'Neil | Australia | Sailing | 1972 Summer, 1976 Summer | |
| John O'Neil | United States | Rugby | 1920 Summer, 1924 Summer | |
| Barry O'Neill | Ireland | Sailing | 1976 Summer | |
| Brandon O'Neill | Canada | Artistic gymnastics | 2008 Summer | |
| Brian O'Neill | United States | Ice hockey | 2018 Winter, 2022 Winter | |
| Darren O'Neill | Ireland | Boxing | 2012 Summer | |
| Frank O'Neill | Australia | Swimming | 1952 Summer | |
| Jennifer O'Neill | Puerto Rico | Basketball | 2020 Summer | |
| John O'Neill | United States | Field hockey | 1996 Summer | |
| Mary O'Neill | Fencing | 1988 Summer, 1992 Summer | |
| Nathan O'Neill | Australia | Road cycling | 2000 Summer | |
| Patrick O'Neill | United States | Handball | 1976 Summer | |
| Sean O'Neill | Table tennis | 1988 Summer, 1992 Summer | |
| Sean O'Neill | Ireland, New Zealand | Rowing | 2008 Summer, 2012 Summer | |
| Shane O'Neill | Australia | Skateboarding | 2020 Summer, 2024 Summer | |
| Susie O'Neill | Swimming | 1992 Summer, 1996 Summer, 2000 Summer | |
| Taylah O'Neill | Freestyle skiing | 2014 Winter | |
| Uma O'Neill | New Zealand | Equestrian jumping | 2020 Summer | |
| George Onekea | United States | Swimming | 1956 Summer | |
| Aycan Önel | Turkey | Athletics | 1960 Summer | |
| Cahit Önel | 1948 Summer, 1952 Summer, 1960 Summer, 1964 Summer | |
| Cemal Öner | Boxing | 1984 Summer | |
| Vanina Oneto | Argentina | Field hockey | 1996 Summer, 2000 Summer, 2004 Summer | |
| Théophile Onfroy | France | Rowing | 2016 Summer | |
| Valentin Onfroy | 2016 Summer | |
| Allen Ong | Malaysia | Swimming | 2000 Summer, 2004 Summer | |
| Ally Ong | Shooting | 1976 Summer | |
| Ong Ching-ming | Chinese Taipei | Alpine skiing | 1984 Winter, 1988 Winter, 1992 Winter | |
| Deborah Ong | Singapore | Sailing | 2008 Summer | |
| Ong Ewe Hock | Malaysia | Badminton | 1996 Summer, 2000 Summer | |
| Jeffrey Ong | Swimming | 1988 Summer, 1992 Summer | |
| Ong Kiat Guan | Singapore | Basketball | 1956 Summer | |
| Leonard Ong | Sailing | 2016 Summer | |
| Ong Mei Lin | Malaysia | Swimming | 1972 Summer | |
| Mylene Ong | Singapore | 2012 Summer | |
| Thomas Ong | Philippines | Judo | 1964 Summer | |
| Tom Ong | Shooting | 1972 Summer, 1976 Summer | |
| Ileana Ongar | Italy | Athletics | 1976 Summer | |
| Franco Ongarato | Road cycling | 1972 Summer | |
| Christine Ongare | Kenya | Boxing | 2020 Summer | |
| Renato Ongari | Italy | Canoe sprint | 1960 Summer | |
| Alex Ongaro | Canada | Track cycling | 1984 Summer | |
| Busanan Ongbamrungphan | Thailand | Badminton | 2020 Summer | |
| Gisèle Ongollo | Gabon | Athletics | 1984 Summer, 1988 Summer | |
| Gabrielle Onguéné | Cameroon | Football | 2012 Summer | |
| Miye Oni | Nigeria | Basketball | 2020 Summer | |
| Chow On-iam | Thailand | Football | 1968 Summer | |
| Étienne Onimus | France | Basketball | 1936 Summer | |
| Boris Onishchenko | Soviet Union | Modern pentathlon | 1968 Summer, 1972 Summer, 1976 Summer | |
| Anatoly Onishchuk | Shooting | 1968 Summer | |
| Junko Onishi | Japan | Swimming | 2000 Summer, 2004 Summer | |
| Katsumasa Onishi | Shooting | 1992 Summer | |
| Kazumi Onishi | Figure skating | 1968 Winter, 1972 Winter | |
| Misaki Onishi | Athletics | 2016 Summer | |
| Yoshihiro Onishi | Rowing | 1964 Summer | |
| Kyriakos Onisiforou | Greece | Athletics | 1972 Summer | |
| Miyabi Onitsuka | Japan | Snowboarding | 2018 Winter, 2022 Winter | |
| Luiz Onmura | Brazil | Judo | 1980 Summer, 1984 Summer, 1988 Summer | |
| Greta Onnela | Finland | Diving | 1928 Summer | |
| Eike Onnen | Germany | Athletics | 2016 Summer | |
| Imke Onnen | 2020 Summer, 2024 Summer | |
| Yuka Ono | Japan | Canoe sprint | 2020 Summer | |
| Hiroshi Ono | Weightlifting | 1972 Summer | |
| Hiroto Ono [ Wikidata ] | Breaking | 2024 Summer | |
| Hitoshi Ono [ Wikidata ] | Baseball | 1996 Summer | |
| Isao Ono | Ice hockey | 1960 Winter, 1964 Winter | |
| Isao Ono | Biathlon | 1968 Winter, 1972 Winter, 1976 Winter | |
| Kiyoko Ono | Artistic gymnastics | 1960 Summer, 1964 Summer | |
| Mayumi Ono | Field hockey | 2008 Summer, 2016 Summer | |
| Misao Ono | Athletics | 1932 Summer | |
| Mitsuki Ono | Snowboarding | 2022 Winter | |
| Ryuji Ono | Athletics | 2004 Summer | |
| Satomi Ono | Ice hockey | 1998 Winter | |
| Seiji Ono | Table tennis | 1988 Summer | |
| Shinji Ono | Football | 2004 Summer | |
| Shohei Ono | Judo | 2016 Summer, 2020 Summer | |
| Shoko Ono | Ice hockey | 2018 Winter | |
| Takashi Ono | Artistic gymnastics | 1952 Summer, 1956 Summer, 1960 Summer, 1964 Summer | |
| Takashi Ono | Judo | 2008 Summer | |
| Yūdai Ōno | Baseball | 2020 Summer | |
| Yumiko Ono | Swimming | 1968 Summer | |
| Yusaku Ono | Weightlifting | 1972 Summer, 1976 Summer | |
| Himeka Onoda | Australia | Rhythmic gymnastics | 2020 Summer | |
| Kazuo Onoda | Japan | Swimming | 1924 Summer | |
| Toshiya Onoda | Bobsleigh | 1998 Winter | |
| Ginwoo Onodera | Skateboarding | 2024 Summer | |
| Kaho Onodera | Curling | 2014 Winter | |
| Shiho Onodera | Football | 1996 Summer | |
| Taishi Onodera | Volleyball | 2020 Summer, 2024 Summer | |
| Henrietta Ónodi | Hungary | Artistic gymnastics | 1992 Summer, 1996 Summer | |
| József Ónody | Swimming | 1908 Summer | |
| Marta Onofre | Portugal | Athletics | 2016 Summer | |
| Rogelio Onofre | Philippines | 1960 Summer, 1964 Summer, 1968 Summer | |
| Constantin Onofrei | Romania | Boxing | 2000 Summer | |
| Taisiia Onofriichuk | Ukraine | Rhythmic gymnastics | 2024 Summer | |
| Tomoko Onogi | Japan | Swimming | 1988 Summer | |
| Ella Onojuvwevwo | Nigeria | Athletics | 2024 Summer | |
| Blessing Onoko | Boxing | 1988 Summer | |
| Mariya Onolbayeva | Russia | Ice hockey | 2010 Winter | |
| Viktoriia Onopriienko | Ukraine | Rhythmic gymnastics | 2020 Summer | |
| Galina Onopriyenko | Unified Team | Handball | 1992 Summer | |
| Pürevjavyn Önörbat | Mongolia | Wrestling | 2012 Summer, 2016 Summer | |
| Bernardo Onori | Italy | Boxing | 1976 Summer | |
| Steve Onosai | Samoa | Rugby sevens | 2024 Summer | |
| Ryoko Onozawa | Japan | Speed skating | 1972 Winter | |
| Ayana Onozuka | Freestyle skiing | 2014 Winter, 2018 Winter | |
| Mārtiņš Onskulis | Latvia | Alpine skiing | 2014 Winter | |
| Vedat Önsoy | Turkey | Boxing | 1984 Summer | |
| Franke Onsrud | Norway | Shooting | 1924 Summer | |
| Jacob Onsrud | 1920 Summer | |
| Raghu Raj Onta | Nepal | Athletics | 1980 Summer | |
| Lombardo Ontiveros | Mexico | Beach volleyball | 2016 Summer | |
| Juraj Ontko | Czechoslovakia | Canoe slalom | 1992 Summer | |
| Kenji Onuma | Japan | Weightlifting | 1956 Summer, 1960 Summer | |
| Ifeoma Onumonu | Nigeria | Football | 2024 Summer | |
| Anyika Onuora | Great Britain | Athletics | 2012 Summer, 2016 Summer | |
| Aydin Onur | Turkey | 1960 Summer | |
| Hilaire Onwanlélé-Ozimo | Gabon | 1992 Summer | |
| Ngozi Onwumere | Nigeria | Bobsleigh | 2018 Winter | |
| Udodi Onwuzurike | Athletics | 2024 Summer | |
| Henry Onwuzuruike | Football | 2000 Summer | |
| Vincent Onyala | Kenya | Rugby sevens | 2020 Summer, 2024 Summer | |
| Mary Onyali-Omagbemi | Nigeria | Athletics | 1988 Summer, 1992 Summer, 1996 Summer, 2000 Summer, 2004 Summer | |
| Frederick Onyancha | Kenya | 1996 Summer | |
| Chioma Onyekwere | Nigeria | 2024 Summer | |
| Emeka Onyemaechi | Judo | 2004 Summer | |
| Josephine Onyia | Spain | Athletics | 2008 Summer | |
| Dismus Onyiego | Kenya | Shooting | 1968 Summer, 1972 Summer | |
| Oleksandr Onyshchenko | Ukraine | Equestrian jumping | 2008 Summer, 2012 Summer | |
| Volodymyr Onyshchenko | Soviet Union | Football | 1972 Summer, 1976 Summer | |
| Isabela Onyshko | Canada | Artistic gymnastics | 2016 Summer | |
| Somporn Onzhim | Thailand | Shooting | 1976 Summer | |
| Reshmie Oogink | Netherlands | Taekwondo | 2016 Summer | |
| Ooi Hock Lim | Malaysia | Athletics | 1968 Summer | |
| May Ooi | Singapore | Swimming | 1992 Summer | |
| Ooi Tze Liang | Malaysia | Diving | 2016 Summer | |
| Appel Ooiman | Netherlands | Rowing | 1928 Summer | |
| Karl Oole | Estonia | Weightlifting | 1936 Summer | |
| Karel Oomen | Belgium | Wrestling | 1960 Summer | |
| Hendrik Ooms | Netherlands | Track cycling | 1936 Summer | |
| Piet Ooms | Swimming, Water polo | 1908 Summer | |
| Willem Ooms | Track cycling | 1920 Summer | |
| Oon Jin Gee | Singapore | Swimming | 1984 Summer, 1988 Summer | |
| Oon Jin Teik | 1984 Summer | |
| Ab Oord | Netherlands | Weightlifting | 1924 Summer | |
| George Ooro | Kenya | Rugby sevens | 2024 Summer | |
| Lorisa Oorzhak | Russia | Wrestling | 2004 Summer | |
| Maxime Van Oost [ Wikidata ] | Belgium | Field hockey | 2024 Summer | |
| Marlies Oostdam | New Zealand | Football | 2008 Summer | |
| Leendert van Oosten [ Wikidata ] | Netherlands | Wrestling | 1908 Summer | |
| Jan Oosterbaan | Volleyball | 1964 Summer | |
| Jack Oosterlaak | South Africa | Athletics | 1920 Summer | |
| Emma Oosterwegel | Netherlands | 2020 Summer, 2024 Summer | |
| Jan Oosthoek | Football | 1924 Summer | |
| Anel Oosthuizen | South Africa | Athletics | 2016 Summer | |
| John Robert Oosthuizen | 2008 Summer | |
| Ryan Oosthuizen | Rugby sevens | 2024 Summer | |
| Soesoe van Oostrom Soede | Netherlands | Water polo | 1936 Summer | |
| Job van Oostrum | Bobsleigh | 1984 Winter | |
| Shigetaka Oyama | Japan | Shooting | 2020 Summer | |
| Vegard Opaas | Norway | Ski jumping | 1984 Winter, 1988 Winter | |
| Alexandra Opachanova | Kazakhstan | Rowing | 2008 Summer | |
| Maksim Opalev | Russia | Canoe sprint | 2000 Summer, 2004 Summer, 2008 Summer | |
| Christy Opara-Thompson | Nigeria | Athletics | 1992 Summer, 1996 Summer | |
| Charity Opara | 1996 Summer, 2000 Summer | |
| Eberechi Opara | Football | 2000 Summer | |
| Jerzy Opara | Poland | Canoe sprint | 1972 Summer, 1976 Summer | |
| Ngozi Opara | Nigeria | Handball | 1992 Summer | |
| Mobi Oparaku | Football | 1996 Summer | |
| Zoltán Opata | Hungary | 1924 Summer | |
| Markus Opatril | Austria | Swimming | 1988 Summer | |
| Stefan Opatril | 1988 Summer | |
| Aleš Opatrný | Czech Republic | Equestrian jumping | 2020 Summer | |
| Jiří Opavský | Czechoslovakia | Road cycling, Track cycling | 1956 Summer | |
| Jacob Opdahl | Norway | Artistic gymnastics | 1912 Summer, 1920 Summer | |
| Nils Opdahl | 1912 Summer | |
| Kåre Opdal | Alpine skiing | 1956 Winter | |
| Englebert Opdebeeck | Belgium | Road cycling | 1968 Summer | |
| Don Opeloge | Samoa | Weightlifting | 2024 Summer | |
| Ele Opeloge | 2008 Summer, 2012 Summer | |
| Mary Opeloge | 2016 Summer | |
| Arina Openysheva | Russia | Swimming | 2016 Summer | |
| Stéphane Operto | Monaco | Road cycling | 1988 Summer | |
| Motu Opetai | Samoa | Rugby sevens | 2024 Summer | |
| Jai Opetaia | Australia | Boxing | 2012 Summer | |
| Anuoluwapo Juwon Opeyori | Nigeria | Badminton | 2020 Summer, 2024 Summer | |
| Roland Opfer | Germany | Rowing | 1996 Summer | |
| Alf Opheim | Norway | Alpine skiing | 1948 Winter, 1952 Winter | |
| Jason Opicho | Kenya | Athletics | 1984 Summer | |
| John Opio | Uganda | Boxing | 1972 Summer | |
| Ferdinand Opitz | Austria | Art competitions | 1928 Summer, 1936 Summer, 1948 Summer | |
| Lucille Opitz | Germany | Speed skating | 2006 Winter | |
| Simone Opitz | East Germany, Germany | Cross country skiing | 1988 Winter, 1992 Winter | |
| Jaroslav Oplt | Czechoslovakia | Rowing | 1920 Summer | |
| Zdeněk Opočenský | Artistic gymnastics | 1920 Summer | |
| Isaac Opoku | Ghana | Table tennis | 1996 Summer | |
| Patience Opokua | 1992 Summer | |
| Samuel Opone | Nigeria | Football | 1968 Summer | |
| Arturo Oporta | Panama | Wrestling | 1988 Summer | |
| Peter Oppegard | United States | Figure skating | 1988 Winter | |
| Craig Oppel | Swimming | 1988 Summer | |
| Hermann von Oppeln-Bronikowski | Germany | Equestrian dressage | 1936 Summer | |
| Britta Oppelt | Rowing | 2004 Summer, 2008 Summer, 2012 Summer | |
| Kurt Oppelt | Austria | Figure skating | 1952 Winter, 1956 Winter | |
| Paul Opperman | Ireland | Athletics | 2000 Summer | |
| Antonio Oppes | Italy | Equestrian jumping | 1960 Summer | |
| Salvatore Oppes | Equestrian jumping, Equestrian eventing | 1952 Summer, 1956 Summer | |
| Luděk Oppl | Czechoslovakia | Fencing | 1924 Summer | |
| Alexander Oppler | Germany | Art competitions | 1928 Summer | |
| Ernst Oppler | 1928 Summer | |
| Emanuel Oppliger | Australia | Snowboarding | 2006 Winter | |
| Paulo Oppliger | Chile | Alpine skiing | 1988 Winter, 1992 Winter | |
| Martine Oppliger-Bouchonneau | Switzerland | Athletics | 1988 Summer | |
| Stefano Oppo | Italy | Rowing | 2016 Summer, 2020 Summer, 2024 Summer | |
| Anișoara Oprea | Romania | Diving | 1996 Summer, 2000 Summer | |
| Elena Oprea | Rowing | 1976 Summer, 1980 Summer | |
| Laura Oprea | 2016 Summer | |
| Marian Oprea | Athletics | 2004 Summer, 2008 Summer, 2016 Summer | |
| Ovidiu Oprea | Cycling mountain bike | 2004 Summer | |
| Vasile Oprea | Handball | 1984 Summer | |
| Nicolae Oprescu | Artistic gymnastics | 1972 Summer, 1976 Summer, 1980 Summer | |
| Deyvid Oprja | Estonia | Alpine skiing | 2006 Winter, 2010 Winter | |
| Allan Opsahl | United States | Ice hockey | 1948 Winter | |
| Morten Opsahl | Norway | Canoe sprint | 1976 Summer | |
| Frank Opsal | Canada | Shooting | 1956 Summer | |
| Helmut Opschruf | Germany | Weightlifting | 1936 Summer | |
| Silje Opseth | Norway | Ski jumping | 2018 Winter, 2022 Winter | |
| Sören Opti | Suriname | Badminton | 2016 Summer, 2024 Summer | |
| Imogene Opton | United States | Alpine skiing | 1952 Winter | |
| Samson Opuakpo | Nigeria | Swimming | 2016 Summer | |
| Adrián Oquendo | Cuba | Rowing | 2016 Summer | |
| Alexandra Oquendo | Puerto Rico | Volleyball | 2016 Summer | |
| Carlos Oquendo | Colombia | Cycling BMX racing | 2012 Summer, 2016 Summer | |
| Gar O'Quinn | United States | Artistic gymnastics | 1960 Summer | |
| Josefine Öqvist | Sweden | Football | 2004 Summer, 2008 Summer | |
| Tomer Or | Israel | Fencing | 2008 Summer | |
| Rita Oraá | Spain | Volleyball | 1992 Summer | |
| Ibrahim Orabi | Egypt | Wrestling | 1936 Summer, 1948 Summer | |
| Abdelrahman Oraby | Boxing | 2016 Summer, 2020 Summer, 2024 Summer | |
| Gianfranco Oradini | Italy | Sailing | 1976 Summer | |
| Ghanim Oraibi | Iraq | Football | 1988 Summer | |
| Hamid Oraibi | Road cycling | 1960 Summer | |
| Orel Oral | Turkey | Swimming | 2000 Summer, 2004 Summer | |
| Aibek Oralbay | Kazakhstan | Boxing | 2024 Summer | |
| Nurbek Oralbay | 2024 Summer | |
| Niilo Orama | Finland | Sailing | 1948 Summer | |
| Juan Pablo Oramas | Mexico | Baseball | 2020 Summer | |
| Robert Oramas | Venezuela | Volleyball | 2020 Summer | |
| Narcisco Orán | Panama | Weightlifting | 1976 Summer | |
| Mitja Oranič | Slovenia | Nordic combined | 2010 Winter, 2014 Winter | |
| John Oravainen | Australia | Swimming | 1964 Summer | |
| Roman Oravec | Czech Republic | Athletics | 2000 Summer | |
| Askar Orazalinov | Kazakhstan | Water polo | 2000 Summer | |
| Olzhas Orazaliyev | Boxing | 2000 Summer | |
| Bauyrzhan Orazgaliyev | Wrestling | 2004 Summer, 2008 Summer | |
| Orban [ Wikidata ] | Belgium | Equestrian driving | 1900 Summer | |
| Alex Orban | United States | Fencing | 1968 Summer, 1972 Summer, 1976 Summer | |
| Árpád Orbán | Hungary | Football | 1964 Summer | |
| Éva Orbán | Athletics | 2004 Summer, 2008 Summer, 2012 Summer | |
| Ferenc Orbán | 1928 Summer | |
| Frank Orban | Belgium | Track cycling | 1984 Summer | |
| József Orbán | Hungary | Wrestling | 1988 Summer | |
| Kurt Orban | United States | Field hockey | 1948 Summer, 1956 Summer | |
| László Orbán | Hungary | Boxing | 1972 Summer | |
| László Orbán | Shooting | 1980 Summer | |
| Nándor von Orbán | Modern pentathlon | 1936 Summer | |
| Rémy Orban | Belgium | Rowing | 1908 Summer | |
| Sándor Orbán | | Boxing | 1976 Summer | |
| Sarah Orban | Canada | Track cycling | 2024 Summer | |
| Hasan Orbay | Turkey | Archery | 2000 Summer, 2004 Summer | |
| David Orbell | Australia | Swimming | 1984 Summer | |
| Rachelle de Orbeta [ Wikidata ] | Puerto Rico | Athletics | 2024 Summer | |
| Ecaterina Orb-Lazăr | Romania | Fencing | 1956 Summer, 1960 Summer | |
| Bernard Orcel | France | Alpine skiing | 1968 Winter, 1972 Winter | |
| Ashleigh Orchard | Ireland | Rugby sevens | 2024 Summer | |
| Simon Orchard | Australia | Field hockey | 2012 Summer, 2016 Summer | |
| William Orchard | Water polo | 1952 Summer, 1956 Summer | |
| Gordon Orchardson | Great Britain | Field hockey | 1908 Summer | |
| László Orczán | Hungary | Track cycling | 1936 Summer | |
| Damian Ordás | Argentina | Rowing | 2000 Summer | |
| Cuthbert Orde | Great Britain | Art competitions | 1932 Summer | |
| Pablo Ordejón | Spain | Fencing | 1960 Summer | |
| Richard Ordemann | Norway | Taekwondo | 2020 Summer, 2024 Summer | |
| Antonina Ordina | Sweden | Cross country skiing | 1994 Winter, 1998 Winter | |
| Tibor Ordina | Hungary | Athletics | 1996 Summer | |
| Vera Ordina | Unified Team | 1992 Summer | |
| Bjart Ording | Norway | Equestrian jumping, Equestrian eventing | 1928 Summer, 1952 Summer | |
| Max Ordman | South Africa | Wrestling | 1960 Summer | |
| Emil Ordnung | Czechoslovakia | Rowing | 1920 Summer | |
| Béla Ordódy | Hungary | Ice hockey | 1928 Winter | |
| Zsuzsa Ördög | Swimming | 1956 Summer | |
| Karl Ördögh | Austria | Field hockey | 1928 Summer, 1948 Summer | |
| Diego Ordóñez | Spain | Athletics | 1920 Summer, 1924 Summer, 1928 Summer | |
| Ignacio Ordóñez | Wrestling | 1984 Summer | |
| Johana Ordóñez | Ecuador | Athletics | 2008 Summer | |
| Saúl Ordóñez | Spain | 2020 Summer | |
| Manuel Ordovás | Equestrian jumping | 1952 Summer | |
| Antonio Oré | Peru | Basketball | 1936 Summer | |
| Martin Ore | Norway | Luge | 1976 Winter | |
| Michele Orecchia | Italy | Road cycling | 1928 Summer | |
| Joseph O'Regan | Great Britain | Water polo | 2012 Summer | |
| Henri Oreiller | France | Alpine skiing | 1948 Winter, 1952 Winter | |
| Ellis O'Reilly | Ireland | Artistic gymnastics | 2016 Summer | |
| Frank O'Reilly | Athletics | 1960 Summer | |
| Gerry O'Reilly | 1988 Summer | |
| Heather O'Reilly | United States | Football | 2004 Summer, 2008 Summer, 2012 Summer | |
| Luke O'Reilly | Great Britain | Alpine skiing | 1968 Winter | |
| Paddy O'Reilly | Ireland | Football | 1924 Summer | |
| Percy O'Reilly | Great Britain | Polo | 1908 Summer | |
| Rory O'Reilly | United States | Track cycling | 1984 Summer | |
| Wilf O'Reilly | Great Britain | Short track speed skating | 1992 Winter, 1994 Winter | |
| Eduardo Orejuela | Ecuador | Swimming | 1968 Summer | |
| Tamara Orejuela | 1968 Summer | |
| Nataliya Orekhova | Russia | Freestyle skiing | 1994 Winter, 1998 Winter, 2002 Winter |
| Ahmet Örel | Turkey | Wrestling | 1992 Summer | |
| Alenka Orel | Slovenia | Sailing | 1996 Summer | |
| Janja Orel | 1996 Summer, 2000 Summer | |
| Carlos Orellana | Mexico | Boxing | 1928 Summer | |
| Marta Orellana | Argentina | Athletics | 1996 Summer | |
| Néstor Orellana | Mexico | Volleyball | 2016 Summer | |
| Miriam Oremans | Netherlands | Tennis | 2000 Summer | |
| Fikret Ören | Turkey | Cross country skiing | 1988 Winter, 1992 Winter | |
| Yaşar Ören | 1968 Winter | |
| Frederic Orendi | Romania | Artistic gymnastics | 1952 Summer, 1964 Summer | |
| Irina Orendi | Athletics | 1928 Summer | |
| Juan Antonio Orenga | Spain | Basketball | 1992 Summer | |
| Gilbert Orengo | Monaco | Fencing | 1960 Summer | |
| Kęstutis Orentas | Soviet Union | Athletics | 1964 Summer | |
| Lyubomir Oresharov | Bulgaria | Canoe sprint | 1960 Summer | |
| Roman Oreshnikov | Russia | Bobsleigh | 2006 Winter, 2010 Winter | |
| Aleksandar Đorđević | Serbia and Montenegro | Basketball | 1996 Summer | |
| Mina Đorđević | Serbia | 2024 Summer | |
| Joe Orewa | Nigeria | Boxing | 1984 Summer | |
| Marcel Orfidan | France | Athletics | 1920 Summer | |
| Joseph Organ | United States | 1920 Summer | |
| Metin Orgarun | Turkey | Judo | 1984 Summer | |
| Gizem Örge | Volleyball | 2024 Summer | |
| Jean-François d'Orgeix | France | Equestrian jumping | 1948 Summer, 1952 Summer | |
| Franco Orgera | Italy | Modern pentathlon | 1936 Summer | |
| Damdinsürengiin Orgodol | Mongolia | Road cycling | 1980 Summer | |
| Olga Orgonista | Hungary | Figure skating | 1932 Winter | |
| Laura Orgué | Spain | Cross country skiing | 2006 Winter, 2010 Winter, 2014 Winter | |
| Andreas Orheim | Norway | Canoe sprint | 1976 Summer | |
| Györgyi Őri | Hungary | Handball | 1980 Summer | |
| Chinedu Oriala | Nigeria | Athletics | 2008 Summer | |
| Andrea Oriana | Italy | Swimming | 1996 Summer | |
| Constanza Oriani | Argentina | Fencing | 1984 Summer | |
| Delicious Orie | Great Britain | Boxing | 2024 Summer | |
| Lasse Orimus | Finland | Athletics | 1976 Summer | |
| Sergey Orin | Tajikistan | Diving | 1996 Summer | |
| André Oriol | France | Rowing | 1924 Summer | |
| Fernand Oriol | 1924 Summer | |
| Veaceslav Oriol | Moldova | Road cycling | 1996 Summer | |
| Christian d'Oriola | France | Fencing | 1948 Summer, 1952 Summer, 1956 Summer, 1960 Summer | |
| Thomas O'Riordan | Ireland | Athletics | 1964 Summer | |
| Farkhod Oripov | Tajikistan | Swimming | 2000 Summer | |
| Valentin Orischenko | Soviet Union | Canoe sprint | 1952 Summer | |
| Samson Oriso | Kenya | Field hockey | 1988 Summer | |
| Tobias Oriwol | Canada | Swimming | 2008 Summer, 2012 Summer | |
| Keturah Orji | United States | Athletics | 2016 Summer, 2020 Summer, 2024 Summer | |
| Angie Orjuela | Colombia | 2016 Summer, 2020 Summer, 2024 Summer | |
| Arabelly Orjuela | 2012 Summer | |
| Ahmet Örken | Turkey | Road cycling | 2016 Summer, 2020 Summer | |
| Pürevdorjiin Orkhon | Mongolia | Wrestling | 2016 Summer, 2024 Summer | |
| Christian Orlainsky | Austria | Alpine skiing | 1980 Winter | |
| Valbjörn Þorláksson | Iceland | Athletics | 1960 Summer, 1964 Summer, 1968 Summer | |
| Carlo Orlandi | Italy | Boxing | 1928 Summer | |
| Giovanni-Battista Orlandi | Athletics | 1920 Summer | |
| Ivo Orlandi | Venezuela | Shooting | 1968 Summer | |
| Vittorio Orlandi | Italy | Equestrian jumping | 1972 Summer | |
| Orlando Paladino Orlandini | Art competitions | 1936 Summer | |
| Rodolfo Orlandini | Argentina | Football | 1928 Summer | |
| Alexandra Orlando | Canada | Rhythmic gymnastics | 2008 Summer | |
| Alfonso Orlando | Italy | Athletics | 1912 Summer | |
| Gaetano Orlando | Ice hockey | 1994 Winter, 1998 Winter | |
| Giovanni Orlando | Swimming | 1964 Summer | |
| John Orlando | Nigeria | Football | 1980 Summer | |
| Sergey Orlenko | Russia | Volleyball | 1996 Summer | |
| Jerzy Woyna Orlewicz | Poland | Alpine skiing | 1964 Winter | |
| Thomas Orley | United States | Fencing | 1964 Summer | |
| Maciej Orlik | Poland | Shooting | 1976 Summer | |
| Marcus Orlob | United States | Equestrian dressage | 2024 Summer | |
| Fred Orlofsky | Artistic gymnastics | 1960 Summer | |
| Andrzej Orłoś | Poland | Equestrian eventing | 1960 Summer | |
| Nikolay Orlov | Russia | Wrestling | 1908 Summer | |
| Vladimir Orlov | Soviet Union | Speed skating | 1964 Winter | |
| Vladimir Nikolayevich Orlov | Russia | Equestrian driving | 1900 Summer | |
| Yevhen Orlov | Ukraine | Wrestling | 2012 Summer | |
| Yuriy Orlov | Sailing | 2004 Summer | |
| Aleksandra Orlova | Russia, Russian Olympic Committee | Freestyle skiing | 2014 Winter, 2018 Winter | |
| Anna Orlova | Latvia | Luge | 1992 Winter, 1994 Winter, 1998 Winter, 2002 Winter, 2006 Winter, 2010 Winter | |
| Kseniya Orlova [ Wikidata ] | Russian Olympic Committee | Freestyle skiing | 2022 Winter | |
| Maria Orlova | Russia | Skeleton | 2014 Winter | |
| Nadezhda Orlova | Bobsleigh | 2006 Winter | |
| Wacław Orłowski | Poland | Wrestling | 1968 Summer | |
| Róbert Örlschléger | Hungary | Rowing | 1972 Summer | |
| Andriy Orlyk | Ukraine | Cross country skiing | 2018 Winter | |
| Carole Ormaca | United States | Figure skating | 1956 Winter | |
| Sándor Ormándi | Hungary | Rowing | 1948 Summer | |
| Bernard Ormanowski | Poland | 1928 Summer | |
| Patricio Ormazábal | Chile | Football | 2000 Summer | |
| Thalia Munro | United States | Water polo | 2004 Summer | |
| Annabelle Orme | Artistic swimming | 2008 Summer | |
| Katie Ormerod | Great Britain | Snowboarding | 2022 Winter | |
| Shelley Ormes [ Wikidata ] | Australia | Handball | 2000 Summer | |
| James Ormond | Great Britain | Alpine skiing | 1998 Winter | |
| Lewis Ormond | New Zealand | Rugby sevens | 2016 Summer | |
| Sophie Ormond | Great Britain | Alpine skiing | 1998 Winter | |
| Mark Ormrod | Australia | Athletics | 2004 Summer, 2008 Summer | |
| Dan Ormsbee | United States | Art competitions | 1932 Summer | |
| Bob Ormsby | Alpine skiing | 1988 Winter | |
| Brett Ormsby | Water polo | 2004 Summer | |
| William Ormston | Great Britain | Track cycling | 1920 Summer | |
| Gunhild Ørn | Norway | Road cycling | 1992 Summer | |
| Mikael Örn | Sweden | Swimming | 1984 Summer | |
| Rolf Örn | Equestrian jumping | 1936 Summer | |
| Hélder Ornelas | Portugal | Athletics | 2000 Summer, 2008 Summer | |
| Suwan Ornkerd | Thailand | Road cycling | 1964 Summer | |
| Jan Ornoch | Poland | Athletics | 1972 Summer, 1976 Summer | |
| Stefan Örnskog | Sweden | Ice hockey | 1994 Winter | |
| Louise Ørnstedt | Denmark | Swimming | 2000 Summer, 2004 Summer | |
| Dion Ørnvold | Football | 1948 Summer | |
| Nahum Orobitg | Andorra | Alpine skiing | 1988 Winter, 1992 Winter | |
| Tarsis Orogot | Uganda | Athletics | 2024 Summer | |
| Oliver Orok | Nigeria | Weightlifting | 1984 Summer | |
| Daniela Oronova | Bulgaria | Rowing | 1988 Summer, 1992 Summer, 1996 Summer | |
| Corneliu Oros | Romania | Volleyball | 1972 Summer, 1980 Summer | |
| Tibor Oross | Hungary | Handball | 1988 Summer | |
| Csaba Orosz | Slovakia | Canoe sprint | 1996 Summer | |
| Dezső Orosz [ Wikidata ] | Hungary | Wrestling | 1912 Summer | |
| Károly Orosz | Ice hockey | 1964 Winter | |
| Miklós Orosz [ Wikidata ] | Wrestling | 1908 Summer | |
| Pál Orosz | Football | 1960 Summer | |
| Irén Orosz-Árva | Athletics | 1972 Summer, 1980 Summer | |
| Aoife O'Rourke | Ireland | Boxing | 2020 Summer, 2024 Summer | |
| Derval O'Rourke | Athletics | 2004 Summer, 2008 Summer, 2012 Summer | |
| Gail O'Rourke | United States | Volleyball | 1964 Summer | |
| James O'Rourke | Canoe sprint | 1936 Summer | |
| James O'Rourke Jr. | 1964 Summer | |
| Mike O'Rourke | New Zealand | Athletics | 1984 Summer | |
| Thomas O'Rourke | United States | Road cycling | 1952 Summer | |
| Aimar Oroz | Spain | Football | 2024 Summer | |
| Alejandra Orozco | Mexico | Diving | 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Alejandro Orózco | Equestrian jumping | 1988 Summer | |
| Armando Orozco | Cuba | Athletics | 1980 Summer | |
| Germán Orozco | Argentina | Field hockey | 2000 Summer, 2004 Summer | |
| John Orozco | United States | Artistic gymnastics | 2012 Summer | |
| Jorge Orozco | Mexico | Shooting | 2020 Summer | |
| José Clemente Orozco | Art competitions | 1932 Summer | |
| Lisseth Orozco | Colombia | Judo | 2004 Summer | |
| Michael Orozco | United States | Football | 2008 Summer | |
| Ruben Orozco | Uruguay | Modern pentathlon | 1948 Summer | |
| William Orpen | Great Britain | Art competitions | 1928 Summer | |
| Georgios Orphanidis | Greece | Shooting | 1896 Summer, 1908 Summer | |
| Brooks Orpik | United States | Ice hockey | 2010 Winter, 2014 Winter | |
| Katrina Orpwood | Australia | Artistic swimming | 2000 Summer | |
| Donald Orr | Canada | Boxing | 2000 Summer | |
| Jenny Orr | Australia | Athletics | 1972 Summer | |
| Lee Orr | Canada | 1936 Summer | |
| Meredith Orr | New Zealand | Field hockey | 2004 Summer | |
| Pete Orr | Canada | Baseball | 2004 Summer | |
| Vickie Orr | United States | Basketball | 1992 Summer | |
| Diana Orrange | Athletics | 1996 Summer | |
| Magne Orre | Norway | Road cycling | 1972 Summer, 1976 Summer | |
| Ariana Orrego | Peru | Artistic gymnastics | 2016 Summer, 2020 Summer | |
| Arne Orrgård | Sweden | Shooting | 1968 Summer | |
| Alessia Orro | Italy | Volleyball | 2016 Summer, 2020 Summer, 2024 Summer | |
| Jiří Orság | Czech Republic | Weightlifting | 2012 Summer, 2016 Summer, 2020 Summer | |
| Günter Orschel | Bulgaria | Equestrian jumping | 2000 Summer | |
| Alessandra Orselli | Italy | Athletics | 1972 Summer | |
| Brian Orser | Canada | Figure skating | 1984 Winter, 1988 Winter | |
| Stalvira Orshush | Russian Olympic Committee | Wrestling | 2020 Summer | |
| Viktoria Orsi Toth | Italy | Beach volleyball | 2020 Summer | |
| Marco Orsi | Swimming | 2012 Summer, 2016 Summer | |
| Ni Orsi Jr. | United States | Alpine skiing | 1964 Winter | |
| Raimundo Orsi | Argentina | Football | 1928 Summer | |
| Lorenzo Orsini | Australia | Weightlifting | 1980 Summer | |
| Piotr Orslowski | Poland | Luge | 1998 Winter | |
| Colleen Orsmond | South Africa | Rowing | 1996 Summer, 2000 Summer | |
| Bruno Orsoni | France | Swimming | 1996 Summer | |
| Riccardo Orsoni [ Wikidata ] | Italy | Athletics | 2024 Summer | |
| Hans-Henrik Ørsted | Denmark | Track cycling | 1980 Summer | |
| Vítězslav Országh | Czechoslovakia | Weightlifting | 1968 Summer | |
| Petra Országhová | Slovakia | Ice hockey | 2010 Winter | |
| Luis Orta | Venezuela | Athletics | 2016 Summer | |
| Luis Orta | Cuba | Wrestling | 2020 Summer, 2024 Summer | |
| Alejandra Ortega | Mexico | Athletics | 2016 Summer, 2024 Summer | |
| Antonio Carlos Ortega | Spain | Handball | 2000 Summer, 2004 Summer | |
| Ariel Ortega | Argentina | Football | 1996 Summer | |
| Cristian Ortega | Colombia | Track cycling | 2024 Summer | |
| David Ortega | Spain | Swimming | 2000 Summer | |
| Francisco Ortega | Argentina | Football | 2020 Summer | |
| Gerardo Ortega | Spain | 1968 Summer | |
| Iván Ortega | Mexico | Modern pentathlon | 1992 Summer | |
| José Ortega | Spain | Boxing | 1988 Summer, 1992 Summer | |
| Mauricio Ortega | Colombia | Athletics | 2016 Summer, 2020 Summer, 2024 Summer | |
| Miguel Ortega | Mexico | Modern pentathlon | 1932 Summer | |
| Norman Ortega | Nicaragua | Shooting | 1992 Summer | |
| Omar Ortega | Argentina | Athletics | 1984 Summer | |
| Orlando Ortega | Cuba, Spain | 2012 Summer, 2016 Summer | |
| Policarpio Ortega | Philippines | Sailing | 1984 Summer | |
| Rafael Ortega | Dominican Republic | Weightlifting | 1976 Summer | |
| Vicente Ortega | Spain | Handball | 1972 Summer | |
| Víctor Ortega | Colombia | Diving | 2008 Summer, 2012 Summer, 2016 Summer | |
| Miguel Ortego | Spain | Field hockey | 1988 Summer, 1992 Summer | |
| Ruben Örtegren | Sweden | Shooting | 1912 Summer | |
| Luciano Ortelli | Italy | Wrestling | 1984 Summer | |
| Dagoberto Ortensi | Art competitions | 1936 Summer, 1948 Summer | |
| Florian Orth | Germany | Athletics | 2016 Summer | |
| György Orth | Hungary | Football | 1924 Summer | |
| Joaquin Orth | Mexico | Equestrian dressage | 1996 Summer | |
| William R. Orthwein | United States | Swimming, Water polo | 1904 Summer | |
| Oscar Ortigosa | Peru | Swimming | 1984 Summer | |
| Venanzio Ortis | Italy | Athletics | 1976 Summer | |
| Abel Ortiz | Argentina | Shooting | 1948 Summer | |
| Alberto Ortiz | Uruguay | Modern pentathlon | 1948 Summer, 1952 Summer | |
| Alejandro Ortiz | Cuba | Basketball | 1976 Summer, 1980 Summer | |
| Alejandro Ortíz | Guatemala | Football | 1988 Summer | |
| Alondra Ortiz [ Wikidata ] | Costa Rica | Swimming | 2024 Summer | |
| Arturo Ortiz | Spain | Athletics | 1988 Summer, 1992 Summer, 1996 Summer | |
| Beatriz Ortiz | Water polo | 2016 Summer, 2020 Summer, 2024 Summer | |
| Carlos Ortiz | Cuba | Wrestling | 2000 Summer | |
| Carlos Ortiz | Mexico | Golf | 2020 Summer, 2024 Summer | |
| Celia Pulido Ortíz [ Wikidata ] | Swimming | 2024 Summer | |
| César Ortíz | Shooting | 1992 Summer | |
| Chris Ortiz | Puerto Rico | Basketball | 2024 Summer | |
| Citlalli Ortiz [ Wikidata ] | Mexico | Boxing | 2024 Summer | |
| Constancio Ortiz | Philippines | Basketball | 1960 Summer | |
| Evaristo Ortíz | Dominican Republic | Athletics | 1988 Summer | |
| Félipe Ortiz | Guatemala | Shooting | 1968 Summer | |
| Fernando Ortiz | Mexico | Athletics | 1932 Summer | |
| Fernando Ortíz | Sailing | 1964 Summer | |
| Fidel Ortiz | Boxing | 1928 Summer, 1936 Summer | |
| Francisco Ortíz | Spain | Diving | 1924 Summer | |
| Gretchen Ortiz | Puerto Rico | Sailing | 2020 Summer | |
| Idalys Ortiz | Cuba | Judo | 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Ignacio Ortiz | Argentina | Field hockey | 2016 Summer, 2020 Summer | |
| Ismael Ortiz | Panama | Swimming | 2004 Summer | |
| Jacqueline Ortiz [ Wikidata ] | Puerto Rico | Softball | 1996 Summer | |
| Jantony Ortiz | Boxing | 2012 Summer | |
| Jesús Ortiz | Cuba | Fencing | 1980 Summer | |
| Jorge Ortíz | Puerto Rico | Athletics | 1976 Summer | |
| José Ortiz | Basketball | 1988 Summer, 1992 Summer, 1996 Summer, 2004 Summer | |
| José Ortiz | Guatemala | Athletics | 2020 Summer | |
| Julio Ortíz | 1968 Summer | |
| Lionel Ortíz | Puerto Rico | Boxing | 1988 Summer | |
| Ludwig Ortiz | Venezuela | Judo | 2000 Summer, 2004 Summer, 2008 Summer | |
| Luis Ortiz | Puerto Rico | Boxing | 1984 Summer | |
| Luis Ortiz | Colombia | Shooting | 1984 Summer | |
| Manuel Ortiz | Cuba | Fencing | 1968 Summer, 1972 Summer, 1976 Summer, 1980 Summer | |
| Mariano Ortiz | Puerto Rico | Basketball | 1968 Summer, 1972 Summer, 1976 Summer | |
| Mario Ortíz | Argentina | Sailing | 1936 Summer | |
| Mario Ortíz | Boxing | 1972 Summer | |
| Mariona Ortiz | Spain | Basketball | 2024 Summer | |
| Matilde Ortiz | Water polo | 2012 Summer, 2016 Summer | |
| Melissa Ortiz | Colombia | Football | 2012 Summer | |
| Mirna Ortiz | Guatemala | Athletics | 2012 Summer, 2016 Summer, 2020 Summer | |
| Nicolas Ortíz | Puerto Rico | Boxing | 1972 Summer | |
| Norman Ortíz | Colombia | Football | 1968 Summer | |
| Nuria Ortiz | Mexico | Shooting | 1968 Summer, 1972 Summer, 1984 Summer, 1988 Summer | |
| Óscar Ortiz | Tennis | 1996 Summer | |
| Pedro Ortíz | Athletics | 1932 Summer | |
| Pedro Ortiz | Colombia | 1988 Summer | |
| Procopio Ortíz | Mexico | Equestrian jumping | 1932 Summer | |
| Ramiro Ortiz | Puerto Rico | Shooting | 1952 Summer | |
| Silvia Ortiz [ Wikidata ] | Ecuador | Athletics | 2024 Summer | |
| Tania Ortiz | Cuba | Volleyball | 1992 Summer | |
| Tatiana Ortiz | Mexico | Diving | 2008 Summer | |
| Vivian Ortiz | Swimming | 1968 Summer | |
| Willington Ortiz | Colombia | Football | 1972 Summer | |
| Yaima Ortiz | Cuba | Volleyball | 2004 Summer, 2008 Summer | |
| Yolanda Ortíz | Diving | 2000 Summer, 2004 Summer | |
| Zuleydis Ortiz | Fencing | 2000 Summer | |
| Bruno Ortiz-Cañavate | Spain | Swimming | 2016 Summer | |
| Miguel Ortiz-Cañavate | 2016 Summer | |
| Patrick Ortlieb | Austria | Alpine skiing | 1992 Winter, 1994 Winter | |
| Günther Ortmann | Germany | Handball | 1936 Summer | |
| Siegfried Ortmann | West Germany | Archery | 1972 Summer | |
| Franz Ortner | Austria | Speed skating | 1936 Winter | |
| Serena Ortolani | Italy | Volleyball | 2008 Summer, 2016 Summer | |
| Armanto Ortolano | Greece | Sailing | 1984 Summer, 1988 Summer, 1992 Summer | |
| Julien d'Ortoli | France | 2016 Summer | |
| Genevieve Orton | Canada | Canoe sprint | 2016 Summer | |
| George Orton | United States | Athletics | 1900 Summer | |
| Fernando Ortuño | Spain | Football | 1968 Summer | |
| Isabel Ortuño | Handball | 2004 Summer | |
| Valeria Ortuño | Mexico | Athletics | 2020 Summer | |
| Alejandro Ortuoste | Philippines | Boxing | 1952 Summer | |
| Stephanie Ortwig | West Germany | Swimming | 1988 Summer | |
| Richard Oruche | Nigeria | Basketball | 2012 Summer | |
| Rustam Orujov | Azerbaijan | Judo | 2012 Summer, 2016 Summer, 2020 Summer | |
| Vugar Orujov | Unified Team, Russia | Wrestling | 1992 Summer, 1996 Summer | |
| Wilson Oruma | Nigeria | Football | 1996 Summer | |
| Mohamad Orungi | Kenya | Boxing | 1988 Summer | |
| Selin Oruz | Germany | Field hockey | 2016 Summer, 2020 Summer, 2024 Summer | |
| Timur Oruz | 2016 Summer, 2020 Summer | |
| Erik Ørvig | Norway | Sailing | 1920 Summer | |
| Olaf Ørvig | 1920 Summer | |
| Thor Ørvig | 1920 Summer | |
| Eva Orvošová | Slovakia | Road cycling, Cycling mountain bike | 1996 Summer | |
| Bernice Orwig | United States | Water polo | 2000 Summer | |
| Elena Oriabinskaia | Russian Olympic Committee | Rowing | 2020 Summer | |
| Assem Orynbay | Kazakhstan | Shooting | 2020 Summer, 2024 Summer | |
| Zbigniew Orywał | Poland | Athletics | 1960 Summer | |
| Martina Orzan | Italy | Rowing | 1996 Summer | |
| Rareş Orzaţa | Romania | Artistic gymnastics | 2000 Summer | |
| Barbara Orzechowska-Ryszel | Poland | Fencing | 1960 Summer | |
| Daniel Orzechowski | Brazil | Swimming | 2012 Summer | |
| Kazimierz Orzeł | Poland | Athletics | 1976 Summer | |
| Alexander Os | Norway | Biathlon | 2010 Winter | |
| Chip Van Os | United States | Handball | 1996 Summer | |
| Yukiko Osada | Japan | Swimming | 2004 Summer | |
| Liliya Osadchaya | Soviet Union | Volleyball | 1976 Summer | |
| Alex Osadchuk | Australia | Water polo | 2004 Summer | |
| Matías Osadczuk | Argentina | Rugby sevens | 2020 Summer, 2024 Summer | |
| Andrew Osagie | Great Britain | Athletics | 2012 Summer | |
| Nafiu Osagie | Nigeria | 1952 Summer | |
| Mansoor Bu Osaiba [ Wikidata ] | United Arab Emirates | Road cycling | 1992 Summer | |
| Naomi Osaka | Japan | Tennis | 2020 Summer, 2024 Summer | |
| Jun Osakada | Athletics | 1996 Summer, 2000 Summer, 2004 Summer | |
| Keiko Osaki | Diving | 1964 Summer, 1968 Summer, 1972 Summer | |
| Sakae Osaki | Athletics | 1992 Summer | |
| Yoshihiko Osaki | Swimming | 1960 Summer | |
| Akinobu Osako | Judo | 1988 Summer | |
| Suguru Osako | Athletics | 2016 Summer, 2020 Summer, 2024 Summer | |
| Daisy Osakue | Italy | 2020 Summer, 2024 Summer | |
| Oskar Osala | Finland | Ice hockey | 2018 Winter | |
| Ahmed Mohamed Osama | Sudan | Table tennis | 1996 Summer | |
| Seiichi Osanai | Japan | Wrestling | 1984 Summer | |
| Chiho Osawa | Ice hockey | 2014 Winter, 2018 Winter, 2022 Winter | |
| Masayo Ōsawa | Diving | 1936 Summer | |
| Masayuki Osawa | Swimming | 1968 Summer | |
| Reiko Ōsawa | Diving | 1936 Summer | |
| Shigetoshi Osawa | Athletics | 1928 Summer | |
| Tetsuo Osawa | Road cycling, Track cycling | 1956 Summer, 1960 Summer | |
| Tomohiro Osawa | Athletics | 1988 Summer | |
| Oludamola Osayomi | Nigeria | 2004 Summer, 2008 Summer, 2012 Summer | |
| Agnes Osazuwa | 2008 Summer, 2016 Summer | |
| Uhunoma Osazuwa | 2012 Summer, 2016 Summer | |
| Harold Osborn | United States | 1924 Summer, 1928 Summer | |
| John Osborn | Great Britain | Sailing | 1976 Summer | |
| Valda Osborn | Figure skating | 1952 Winter | |
| Alexander Osborne | United States | Rowing | 2012 Summer | |
| Coulter Osborne | Canada | Basketball | 1956 Summer | |
| Frederick Osborne [ Wikidata ] | Great Britain | Boxing | 1908 Summer | |
| Hannah Osborne | New Zealand | Rowing | 2020 Summer | |
| Jason Osborne | Germany | 2016 Summer, 2020 Summer | |
| Rowan Osborne | Great Britain | Canoe slalom | 1972 Summer | |
| Manuel Osborne-Paradis | Canada | Alpine skiing | 2006 Winter, 2010 Winter, 2014 Winter, 2018 Winter | |
| Carl Osburn | United States | Shooting | 1912 Summer, 1920 Summer, 1924 Summer | |
| Ruth Osburn | Athletics | 1932 Summer | |
| Roberto Oscal | Guatemala | 1996 Summer | |
| Oscar | Brazil | Football | 2012 Summer | |
| Ricardo Oscare | Argentina | Biathlon | 2002 Winter | |
| Fernando Oscaris | Field hockey | 2000 Summer | |
| Henri van Osch | Netherlands | Swimming | 1964 Summer | |
| Matthieu Osch | Luxembourg | Alpine skiing | 2018 Winter, 2022 Winter | |
| Cornelia Oschkenat | East Germany | Athletics | 1988 Summer | |
| Wolf-Dieter Oschlies | West Germany | Rowing | 1976 Summer | |
| Manuela Oschmann | Germany | Cross country skiing | 1992 Winter | |
| Felix Oschmautz | Austria | Canoe slalom | 2020 Summer, 2024 Summer | |
| Emmanuel Osei Kuffour | Ghana | Football | 1996 Summer | |
| Emmanuel Osei | 2004 Summer | |
| Kennedy Osei | Athletics | 1992 Summer | |
| Sandy Osei-Agyemang | 1972 Summer | |
| Julio César Osejo [ Wikidata ] | Nicaragua | Baseball | 1996 Summer | |
| Dmytro Oseledets | Ukraine | Swimming | 2016 Summer | |
| Diego Osella | Argentina | Basketball | 1996 Summer | |
| Otto Osen | Norway | Athletics | 1912 Summer | |
| Tinus Osendarp | Netherlands | 1936 Summer | |
| Bartosz Osewski | Poland | 2012 Summer | |
| Ann Osgerby | Great Britain | Swimming | 1980 Summer, 1984 Summer | |
| Janet Osgerby | 1980 Summer | |
| Tim O'Shannessey | Australia | Track cycling | 1996 Summer | |
| Vitaliy Osharov | Ukraine | Fencing | 2004 Summer | |
| Niall O'Shaughnessy | Ireland | Athletics | 1976 Summer | |
| Stepan Oshchepkov | Soviet Union | Canoe sprint | 1964 Summer | |
| Caroline O'Shea | Ireland | Athletics | 1984 Summer | |
| Danny O'Shea | Canada | Ice hockey | 1968 Winter | |
| Glenn O'Shea | Australia | Track cycling | 2012 Summer, 2016 Summer | |
| Greg O'Shea | Ireland | Rugby sevens | 2020 Summer | |
| Mick O'Shea | Athletics | 1980 Summer | |
| Richard O'Shea | Sailing | 1972 Summer | |
| William O'Shea | Boxing | 1928 Summer | |
| T. J. Oshie | United States | Ice hockey | 2014 Winter | |
| Misaki Oshigiri | Japan | Speed skating | 2014 Winter, 2018 Winter, 2022 Winter | |
| Modupe Oshikoya | Nigeria | Athletics | 1972 Summer | |
| Hiroko Oshima | Japan | Canoe sprint | 1964 Summer | |
| Hiroyuki Oshima | Bobsleigh | 1994 Winter | |
| Kenkichi Oshima | Athletics | 1932 Summer, 1936 Summer | |
| Koichi Oshima | Baseball | 1992 Summer | |
| Kyoko Oshima | Artistic gymnastics | 2004 Summer, 2008 Summer | |
| Megumi Oshima | Athletics | 2000 Summer, 2004 Summer | |
| Ryota Oshima | Football | 2016 Summer | |
| Yasukuni Oshima | Basketball | 1960 Summer | |
| Misaki Oshiro | Weightlifting | 2008 Summer | |
| Rod Oshita | United States | Handball | 1984 Summer, 1988 Summer | |
| Yukiharu Oshita | Japan | Water polo | 1972 Summer | |
| Asisat Oshoala | Nigeria | Football | 2024 Summer | |
| Muwiya Oshode | 1968 Summer | |
| Emmanuel Oshomah | Weightlifting | 1984 Summer | |
| Olufunke Oshonaike | Table tennis | 1996 Summer, 2000 Summer, 2004 Summer, 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer | |
| Eugenia Osho-Williams | Sierra Leone | Athletics | 1980 Summer, 1984 Summer | |
| Alan Oshyer | Australia | Weightlifting | 1960 Summer | |
| Andrzej Osiecimski-Czapski | Poland | Rowing | 1924 Summer | |
| Stefan Osiecki | Art competitions | 1932 Summer | |
| Ellen Osiier | Denmark | Fencing | 1924 Summer | |
| Ivan Joseph Martin Osiier | 1908 Summer, 1912 Summer, 1920 Summer, 1924 Summer, 1928 Summer, 1932 Summer, 1948 Summer | |
| Ivica Osim | Yugoslavia | Football | 1964 Summer | |
| Matías Osinalde | Argentina | Shooting | 1924 Summer | |
| Winand Osiński | Poland | Athletics | 1952 Summer | |
| Denis Osipau | Belarus | Freestyle skiing | 2014 Winter | |
| Denis Osipov | China | Ice hockey | 2022 Winter | |
| Leonid Osipov | Soviet Union | Water polo | 1964 Summer, 1968 Summer, 1972 Summer | |
| Sergey Osipov | Luge | 1972 Winter | |
| Elena Osipova | Russian Olympic Committee | Archery | 2020 Summer | |
| Irina Osipova | Russia | Basketball | 2004 Summer, 2008 Summer, 2012 Summer | |
| Svetlana Osipova | Uzbekistan | Taekwondo | 2020 Summer, 2024 Summer | |
| Tatyana Osipova | Kazakhstan | Cross country skiing | 2010 Winter, 2014 Winter | |
| Iuri Osip'ovi | Soviet Union | Fencing | 1956 Summer | |
| Albina Osipowich | United States | Swimming | 1928 Summer | |
| Guntis Osis | Soviet Union | Bobsleigh | 1988 Winter | |
| Shelayna Oskan-Clarke | Great Britain | Athletics | 2016 Summer | |
| Elisabeth Osl | Austria | Cycling mountain bike | 2008 Summer, 2012 Summer | |
| Paul Osland | Canada | Athletics | 1988 Summer | |
| Abdourahman Osman | Djibouti | Swimming | 2012 Summer | |
| Abrar Osman | Eritrea | Athletics | 2012 Summer, 2016 Summer | |
| Amro El-Sayed Osman | Egypt | Field hockey | 1992 Summer | |
| Farida Osman | Swimming | 2012 Summer, 2016 Summer, 2020 Summer | |
| Gamil Osman | Football | 1920 Summer | |
| Ibrahim Osman | Lebanon | Fencing | 1960 Summer, 1964 Summer | |
| Mohamed Ahmed Osman | Egypt | Wrestling | 1948 Summer, 1952 Summer | |
| Mohamed Hamdi Osman | Basketball | 1976 Summer | |
| Mohamed Hassan bin Osman | Malaysia | Athletics | 1972 Summer | |
| Zaki Osman | Egypt | Football | 1920 Summer | |
| Mustafa Osmanlı | Turkey | Road cycling | 1948 Summer | |
| Şeref Osmanoğlu | Ukraine, Turkey | Athletics | 2012 Summer, 2016 Summer | |
| Adil Osmanov | Moldova | Judo | 2024 Summer | |
| Sihamir Osmanov | North Macedonia | Wrestling | 2004 Summer | |
| Alek Osmanović | Croatia | Bobsleigh | 2006 Winter | |
| Miloslav Ošmera | Czechoslovakia | Ice hockey | 1952 Winter | |
| Nataša Osmokrović | Croatia | Volleyball | 2000 Summer | |
| Bekzat Osmonaliev | Kyrgyzstan | Weightlifting | 2012 Summer | |
| Kanybek Osmonaliyev | Soviet Union | 1980 Summer | |
| Kaetlyn Osmond | Canada | Figure skating | 2014 Winter, 2018 Winter | |
| Asbjørn Osnes | Norway | Ski jumping | 1956 Winter | |
| Gelegjamtsyn Ösökhbayar | Mongolia | Wrestling | 2004 Summer | |
| Vladimir Osokin | Soviet Union | Track cycling | 1976 Summer, 1980 Summer | |
| Liván Osoria | Cuba | Volleyball | 2016 Summer | |
| Aitor Osorio | Andorra | Swimming | 1996 Summer | |
| Camila Osorio | Colombia | Tennis | 2020 Summer, 2024 Summer | |
| Diego Osorio | Football | 1992 Summer | |
| Georgina Osorio | Panama | Swimming | 1976 Summer | |
| Julio Osorio | Basketball | 1968 Summer | |
| Erick Osornio | Mexico | Taekwondo | 2012 Summer | |
| Matic Osovnikar | Slovenia | Athletics | 2000 Summer, 2004 Summer, 2008 Summer | |
| Serhiy Osovych | Ukraine | 1996 Summer | |
| Filip Ospalý | Czech Republic | Triathlon | 2000 Summer, 2004 Summer, 2008 Summer | |
| Oskar Ospelt | Liechtenstein | Athletics | 1936 Summer | |
| Diana Ospina | Colombia | Football | 2016 Summer | |
| Pedro Ospina | 1968 Summer | |
| Elena Ospitaletche | Uruguay | Swimming | 1976 Summer | |
| Felicia Ospitaletche | 1968 Summer, 1972 Summer | |
| Honey Osrin | Great Britain | 2024 Summer | |
| Arnold Oss | United States | Ice hockey | 1952 Winter | |
| Juan Carlos de la Ossa | Spain | Athletics | 2008 Summer | |
| Matylda Ossadnik | Poland | Artistic gymnastics | 1936 Summer | |
| Christopher Ossai | Nigeria | Boxing | 1980 Summer, 1984 Summer | |
| Abdelrahman Ossama | Egypt | Taekwondo | 2012 Summer | |
| Adolphe Osselaer | Belgium | Wrestling | 1936 Summer | |
| Nicolas Osseland | France | Figure skating | 1998 Winter | |
| Friedhelm Osselmann | Germany | Water polo | 1956 Summer, 1960 Summer | |
| Rainer Osselmann | West Germany | 1984 Summer, 1988 Summer | |
| Esmeralda Ossendrijver | Netherlands | Short track speed skating | 1994 Winter | |
| Stanislav Ossinskiy | Kazakhstan | Swimming | 2004 Summer, 2008 Summer | |
| Helmer Osslund | Sweden | Art competitions | 1932 Summer | |
| John Ossowski | Canada | Rowing | 1988 Summer | |
| Alfred Ost | Belgium | Art competitions | 1920 Summer | |
| Isabell Ost | Germany | Speed skating | 2010 Winter | |
| Ahmad Al-Osta | Syria | Wrestling | 1992 Summer, 1996 Summer | |
| Walter Osta | Italy | Freestyle skiing | 1992 Winter, 1994 Winter | |
| Marian Ostafiński | Poland | Football | 1972 Summer | |
| Sergey Ostapchuk | Russia | Swimming | 1996 Summer, 2000 Summer | |
| Aleksey Ostapenko | Volleyball | 2008 Summer | |
| Jeļena Ostapenko | Latvia | Tennis | 2016 Summer, 2020 Summer, 2024 Summer | |
| Igor Ostashov | Soviet Union | Speed skating | 1964 Winter | |
| Cecilia Östberg | Sweden | Ice hockey | 2010 Winter, 2014 Winter | |
| Frida Östberg | Football | 2004 Summer, 2008 Summer | |
| Gunnar Östberg | Cross country skiing | 1952 Winter | |
| Mikael Östberg | 2006 Winter | |
| Søren Østberg | Denmark | Swimming | 1984 Summer | |
| Hilde Østbø | Norway | Handball | 1996 Summer | |
| Einar Østby | Cross country skiing | 1960 Winter, 1964 Winter | |
| Knut Østby | Canoe sprint | 1948 Summer, 1952 Summer, 1956 Summer | |
| Shyril O'Steen | United States | Rowing | 1984 Summer | |
| Kåre Østensen | Norway | Ice hockey | 1964 Winter, 1968 Winter, 1972 Winter | |
| Nils Östensson | Sweden | Cross country skiing | 1948 Winter | |
| Adalbert Oster | Romania | Shooting | 1976 Summer | |
| Stellan Österberg | Sweden | Badminton | 1992 Summer | |
| André Osterberger | France | Athletics | 1952 Summer | |
| Bror Österdahl | Sweden | 1924 Summer | |
| Maire Österdahl | Finland | 1952 Summer | |
| Jan Østergaard | Denmark | Cycling mountain bike | 1996 Summer | |
| Micha Østergaard | Swimming | 2008 Summer | |
| Trine Østergaard | Handball | 2024 Summer | |
| Wedell Østergaard | Road cycling | 1952 Summer | |
| Maria Östergren | Sweden | Cycling mountain bike | 2004 Summer | |
| Mary Ostergren | United States | Biathlon | 1992 Winter, 1994 Winter | |
| Nestor Östergren | Sweden | Rowing | 1920 Summer | |
| Claudia Österheld | West Germany | Canoe sprint | 1988 Summer | |
| Bernt Østerkløft | Norway | Nordic combined | 1936 Winter | |
| Tommy Österlund | Sweden | Rowing | 1992 Summer | |
| Anja Osterman | Slovenia | Canoe sprint | 2020 Summer | |
| Cat Osterman | United States | Softball | 2004 Summer, 2008 Summer, 2020 Summer | |
| Elisabeth Ostermeyer | Germany | Artistic gymnastics | 1952 Summer | |
| Micheline Ostermeyer | France | Athletics | 1948 Summer | |
| Henrik Østervold | Norway | Sailing | 1920 Summer | |
| Jan Østervold | 1920 Summer | |
| Kristian Østervold | 1920 Summer | |
| Ole Østervold | 1920 Summer | |
| Walter Osterwalder | Switzerland | Rowing | 1960 Summer | |
| Heinz Ostheimer | Saar | Artistic gymnastics | 1952 Summer | |
| Sten Osther | Norway | Handball | 1972 Summer | |
| Oscar Osthoff | United States | Weightlifting | 1904 Summer | |
| René Osthold | Germany | Shooting | 1992 Summer | |
| Frank Ostholt | Equestrian eventing | 2004 Summer, 2008 Summer | |
| Renzo Ostino | Italy | Rowing | 1960 Summer | |
| Marko Oštir | Slovenia | Handball | 2004 Summer | |
| Andreas Ostler | Germany | Bobsleigh | 1952 Winter, 1956 Winter | |
| Ingrid Ostler | Austria | Figure skating | 1964 Winter | |
| Anna Östling | Sweden | Sailing | 2012 Summer | |
| Gustav Östling | Athletics | 1948 Summer, 1952 Summer | |
| Maria Östling | Swimming | 1996 Summer, 2004 Summer | |
| Sebastian Östling | Sailing | 2008 Summer, 2012 Summer | |
| Stig Östling | Ice hockey | 1972 Winter | |
| Anita Östlund | Figure skating | 2018 Winter | |
| Benny Östlund | Shooting | 1988 Summer, 1992 Summer | |
| Marie-Helene Östlund | Cross country skiing | 1988 Winter, 1992 Winter, 1994 Winter | |
| Arvid Östman | Wrestling | 1924 Summer | |
| Bror Östman | Ski jumping | 1952 Winter, 1956 Winter | |
| Mats Östman | 1968 Winter | |
| Ole Østmo | Norway | Shooting | 1900 Summer | |
| Juan Ostoic | Chile | Basketball | 1952 Summer, 1956 Summer | |
| Stanisław Ostoja-Chrostowski | Poland | Art competitions | 1936 Summer | |
| Đuro Ostojić | Serbia and Montenegro | Basketball | 2004 Summer | |
| Milica Ostojić | Serbia | Swimming | 2008 Summer | |
| María Ostolaza | Peru | Volleyball | 1976 Summer | |
| Luis Ostos | Athletics | 2016 Summer | |
| Axel Östrand | Sweden | Ski jumping | 1936 Winter | |
| Erik Østrand | Denmark | Wrestling | 1952 Summer | |
| Per-Olof Östrand | Sweden | Swimming | 1948 Summer, 1952 Summer, 1956 Summer | |
| Marián Ostrčil | Slovakia | Canoe sprint | 2004 Summer, 2008 Summer | |
| Mário Ostrčil | 2000 Summer | |
| Kjeld Østrøm | Denmark | Rowing | 1956 Summer | |
| Krystyna Ostromęcka | Poland | Volleyball | 1968 Summer | |
| Sergey Ostroshapkin | Belarus | Boxing | 1996 Summer | |
| Adam Ostrowski | Poland | Wrestling | 1968 Summer, 1972 Summer, 1976 Summer | |
| Karol Ostrowski | Swimming | 2020 Summer | |
| Ryszard Ostrowski | Athletics | 1988 Summer | |
| Stéphane Ostrowski | France | Basketball | 1984 Summer | |
| Lauritz Christian Østrup | Denmark | Fencing | 1908 Summer, 1912 Summer | |
| Lars Andreas Østvik | Norway | Nordic combined | 2002 Winter | |
| Klaus Ostwald | East Germany | Ski jumping | 1980 Winter, 1984 Winter | |
| Ronny Ostwald | Germany | Athletics | 2004 Summer | |
| Dariusz Osuch | Poland | Weightlifting | 1992 Summer, 1996 Summer | |
| Sayuri Osuga | Japan | Speed skating, Track cycling | 2002 Winter, 2004 Summer, 2006 Winter | |
| Emmanuel Osuigwe | Nigeria | Football | 1980 Summer | |
| Chinedum Osuji | Trinidad and Tobago | Taekwondo | 2004 Summer | |
| Christian O'Sullivan | Norway | Handball | 2020 Summer, 2024 Summer | |
| Gillian O'Sullivan | Ireland | Athletics | 2000 Summer | |
| John O'Sullivan | Australia | Road cycling | 1956 Summer | |
| Marcus O'Sullivan | Ireland | Athletics | 1984 Summer, 1988 Summer, 1992 Summer, 1996 Summer | |
| Maurice O'Sullivan | Great Britain | Boxing | 1972 Summer | |
| Rachel Kealaonapua O'Sullivan | United States | Diving | 1968 Summer | |
| Seán O'Sullivan | Ireland | Art competitions | 1932 Summer | |
| Shawn O'Sullivan | Canada | Boxing | 1984 Summer | |
| Sonia O'Sullivan | Ireland | Athletics | 1992 Summer, 1996 Summer, 2000 Summer, 2004 Summer | |
| Sophie O'Sullivan | 2024 Summer | |
| Vince O'Sullivan | United States | 1984 Summer | |
| Isagi Osumi | Japan | Swimming | 1964 Summer | |
| César Osuna | Mexico | Volleyball | 1968 Summer | |
| Sarah Osvath | Australia | Fencing | 1996 Summer | |
| Alfons Oswald | Switzerland | Sailing | 1948 Summer | |
| Denis Oswald | Rowing | 1968 Summer, 1972 Summer, 1976 Summer | |
| Mihael Oswald | Yugoslavia | Artistic gymnastics | 1924 Summer | |
| Pascal Oswald | Switzerland | Skeleton | 2010 Winter | |
| Philipp Oswald | Austria | Tennis | 2020 Summer | |
| Roy Oswalt | United States | Baseball | 2000 Summer | |
| Simone Osygus | Germany | Swimming | 1992 Summer, 1996 Summer | |
| Inna Osypenko-Radomska | Ukraine, Azerbaijan | Canoe sprint | 2000 Summer, 2004 Summer, 2008 Summer, 2012 Summer, 2016 Summer | |
| Morgane Osyssek | France | Artistic gymnastics | 2024 Summer | |
| István Osztrics | Hungary | Fencing | 1972 Summer, 1976 Summer, 1980 Summer | |
| Akira Ōta | Japan | Wrestling | 1984 Summer, 1988 Summer, 1992 Summer | |
| Kaiya Ota | Track cycling | 2024 Summer | |
| Kazuomi Ota | Weightlifting | 2012 Summer | |
| Miwa Ota | Cross country skiing | 1992 Winter | |
| Nobuko Ota | Rowing | 1992 Summer | |
| Shinichi Ota | Track cycling | 2000 Summer | |
| Shinobu Ota | Wrestling | 2016 Summer | |
| Shumin Ota | Art competitions | 1936 Summer | |
| Takuya Ōta | Wrestling | 1996 Summer | |
| Tomio Ota | Athletics | 1960 Summer, 1964 Summer | |
| Yuki Ota | Fencing | 2004 Summer, 2008 Summer, 2012 Summer, 2016 Summer | |
| Rhema Otabor | Bahamas | Athletics | 2024 Summer | |
| Karel Otáhal | Czechoslovakia | Art competitions | 1948 Summer | |
| Martin Otáhal | Czech Republic | Canoe sprint | 1996 Summer | |
| Stanislav Otáhal | Czechoslovakia | Athletics | 1936 Summer | |
| Zdeněk Otáhal | Weightlifting | 1960 Summer, 1964 Summer | |
| Mukhlid Al-Otaibi | Saudi Arabia | Athletics | 2008 Summer, 2012 Summer, 2016 Summer | |
| Sultan Al-Otaibi | Kuwait | Swimming | 1988 Summer, 1992 Summer, 1996 Summer, 2000 Summer | |
| Talak Al-Otaibi | Saudi Arabia | Shooting | 1984 Summer | |
| Tomomi Otaka | Japan | Cross country skiing, Biathlon | 1998 Winter, 2002 Winter, 2006 Winter | |
| Yukiko Otaka | Swimming | 1956 Summer | |
| Yuko Otaka | Luge | 1972 Winter | |
| Hideyuki Otake | Volleyball | 1992 Summer | |
| Nami Otake | Football | 1996 Summer | |
| Chika Otaki | Ice hockey | 2022 Winter | |
| Christopher Otambo | Kenya | Field hockey | 1984 Summer, 1988 Summer | |
| Nicolás Otamendi | Argentina | Football | 2024 Summer | |
| Mio Otani | Japan | 2004 Summer | |
| Sachiko Otani | Volleyball | 1984 Summer | |
| Dzhamal Otarsultanov | Russia | Wrestling | 2012 Summer | |
| Bogdan Laurentiu Otavă | Romania | Bobsleigh | 2014 Winter | |
| Francisco Otayza | Peru | Shooting | 1956 Summer | |
| Martin Otčenáš | Slovakia | Cross country skiing, Biathlon | 2006 Winter, 2014 Winter, 2018 Winter | |
| Natalya Otchenash | Ukraine | Biathlon | 2014 Winter | |
| Marie Oteiza | France | Modern pentathlon | 2020 Summer, 2024 Summer | |
| Oteng Oteng | Botswana | Boxing | 2012 Summer | |
| Andrija Otenhajmer | Yugoslavia | Athletics | 1952 Summer | |
| Carlos Otero | Argentina | Rowing | 1968 Summer | |
| Carolina García Otero [ Wikidata ] | Spain | Canoe sprint | 2024 Summer | |
| Eduardo Germán Otero | Argentina | Swimming | 2000 Summer, 2004 Summer, 2008 Summer | |
| Luis Otero | Spain | Football | 1920 Summer | |
| Matías Otero [ Wikidata ] | Uruguay | Canoe sprint | 2024 Summer | |
| Pedro Otero | Cuba | Basketball | 1948 Summer | |
| Jargalyn Otgon | Mongolia | Archery | 1992 Summer, 1996 Summer | |
| Munkhtsetseg Otgon [ Wikidata ] | Judo | 2020 Summer | |
| Lkhagvasürengiin Otgonbaatar | 2016 Summer, 2020 Summer | |
| Luvsanlkhündegiin Otgonbayar | Athletics | 2004 Summer, 2012 Summer, 2016 Summer | |
| Ravsalyn Otgonbayar | Boxing | 1976 Summer, 1980 Summer | |
| Baatarkhuyagiin Otgonbold | Archery | 2020 Summer, 2024 Summer | |
| Dorjnyambuugiin Otgondalai | Boxing | 2016 Summer | |
| Dolgorjavyn Otgonjargal | Wrestling | 2024 Summer | |
| Naidangiin Otgonjargal | 2008 Summer | |
| Chinbatyn Otgontsetseg | Cross country skiing | 2014 Winter, 2018 Winter | |
| Davaasükhiin Otgontsetseg | Wrestling | 2012 Summer | |
| Otgontsetseg Galbadrakh | Kazakhstan | Judo | 2016 Summer, 2020 Summer | |
| Othman Abdullah | Malaysia | Football | 1972 Summer | |
| Ahmed Othman | Egypt | Wrestling | 2016 Summer | |
| Bacent Othman | Table tennis | 2000 Summer | |
| Jamal Othman | Switzerland | Figure skating | 2006 Winter | |
| Khaled Othman | Libya | Athletics | 1996 Summer | |
| Naceur Ben Othman | Tunisia | Volleyball | 1972 Summer | |
| Naser Al-Othman | Kuwait | Football | 2000 Summer | |
| Alvin Otieno | Kenya | Rugby sevens | 2020 Summer | |
| Eric Otieno | Field hockey | 1984 Summer | |
| Irene Otieno | Rugby sevens | 2016 Summer | |
| Joseph Otieno | Athletics | 1984 Summer | |
| Stacy Otieno | Rugby sevens | 2016 Summer | |
| Joel Otim | Uganda | Athletics | 1992 Summer | |
| Charles Otis | Canada | Fencing | 1936 Summer | |
| Mawupemon Otogbe | Togo | Swimming | 2020 Summer | |
| Keisuke Otoguro | Japan | Wrestling | 2020 Summer | |
| Takuto Otoguro | 2020 Summer | |
| Kouadio Otokpa | Ivory Coast | Athletics | 1984 Summer | |
| Ai Ōtomo | Japan | Volleyball | 2004 Summer, 2012 Summer | |
| Tsutsumi Otomo | Ice hockey | 1998 Winter | |
| Danielle O'Toole-Trejo | Mexico | Softball | 2020 Summer | |
| Dermot O'Toole | Ireland | Art competitions | 1948 Summer | |
| Eddie O'Toole | United States | Athletics | 1948 Summer | |
| Gary O'Toole | Ireland | Swimming | 1988 Summer, 1992 Summer | |
| Maureen O'Toole | United States | Water polo | 2000 Summer | |
| Niall O'Toole | Ireland | Rowing | 1992 Summer, 1996 Summer, 2004 Summer | |
| Kumi Otoshi | Japan | Athletics | 2012 Summer | |
| Svetla Otsetova | Bulgaria | Rowing | 1976 Summer, 1980 Summer | |
| Hiromi Ōtsu | Japan | Speed skating | 2006 Winter | |
| Shinji Otsu | Sailing | 1992 Summer | |
| Yūki Ōtsu | Football | 2012 Summer | |
| Masashi Otsubo | Athletics | 1964 Summer | |
| Toshimitsu Otsubo | Ice hockey | 1968 Winter, 1972 Winter, 1976 Winter | |
| Toshio Otsubo | Diving | 1964 Summer, 1968 Summer | |
| Masahiko Otsue | Alpine skiing | 1972 Winter | |
| Mihoko Otsue | 1968 Winter | |
| Hirofumi Otsuka | Speed skating | 1968 Winter | |
| Hiroko Otsuka | Rhythmic gymnastics | 1988 Summer | |
| Miyako Ōtsuka | Basketball | 1976 Summer | |
| Miyu Otsuka | Swimming | 2012 Summer | |
| Shiho Otsuka | Field hockey | 2012 Summer | |
| Tadashi Ōtsuka | Badminton | 2004 Summer, 2008 Summer | |
| Takeru Otsuka | Snowboarding | 2022 Winter | |
| Tatsunori Otsuka | Volleyball | 2020 Summer, 2024 Summer | |
| Anastasiya Ott | Russia | Athletics | 2008 Summer | |
| Hans Ott | Switzerland | Ice hockey | 1956 Winter | |
| Kurt Ott | Road cycling | 1936 Summer | |
| Ludwig Ott | West Germany | Water polo | 1968 Summer | |
| Martin Ott | Switzerland | Handball | 1984 Summer | |
| Mirjam Ott | Curling | 2002 Winter, 2006 Winter, 2010 Winter, 2014 Winter | |
| Niko Ott | West Germany | Rowing | 1968 Summer | |
| Patricia Ott | Field hockey | 1984 Summer | |
| Paolo Ottavi | Italy | Artistic gymnastics | 2012 Summer | |
| Alfonso Ottaviani | Modern pentathlon | 1964 Summer | |
| Fabrizia D'Ottavio | Rhythmic gymnastics | 2004 Summer, 2008 Summer | |
| Katharina Otte | Germany | Field hockey | 2012 Summer, 2016 Summer | |
| Tarren Otte | Australia | Artistic swimming | 2008 Summer, 2012 Summer | |
| Joris Otten | Netherlands | Canoe slalom | 2024 Summer | |
| Louis Otten | Football | 1908 Summer | |
| Anne Ottenbrite | Canada | Swimming | 1984 Summer | |
| Joseph Otterbeen | Belgium | Athletics | 1920 Summer | |
| Payton Otterdahl | United States | 2020 Summer, 2024 Summer | |
| Suzanne Otterson | Great Britain | Figure skating | 1992 Winter | |
| Hein Otterspeer | Netherlands | Speed skating | 2022 Winter | |
| Henrik Ottesen | Denmark | Boxing | 1956 Summer | |
| Jeanette Ottesen | Swimming | 2004 Summer, 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer | |
| Lasse Ottesen | Norway | Ski jumping | 1992 Winter, 1994 Winter, 1998 Winter | |
| Merlene Ottey | Jamaica, Slovenia | Athletics | 1980 Summer, 1984 Summer, 1988 Summer, 1992 Summer, 1996 Summer, 2000 Summer, 2004 Summer | |
| Milton Ottey | Canada | 1984 Summer, 1988 Summer | |
| Tom Ottey | United States | 1932 Summer | |
| Alex Ottiano | Judo | 2000 Summer, 2004 Summer | |
| Sven Ottke | West Germany, Germany | Boxing | 1988 Summer, 1992 Summer, 1996 Summer | |
| David Ottley | Great Britain | Athletics | 1980 Summer, 1984 Summer, 1988 Summer | |
| Andreas Otto | East Germany, Germany | Boxing | 1988 Summer, 1992 Summer | |
| Anita Otto | East Germany | Athletics | 1968 Summer | |
| Björn Otto | Germany | 2012 Summer | |
| Evelyn Otto | Palau | Swimming | 2004 Summer | |
| Frank Otto | West Germany, Germany | Water polo | 1984 Summer, 1988 Summer, 1992 Summer | |
| Fred Otto | Germany | Art competitions | 1936 Summer | |
| Gisela Otto | West Germany | Luge | 1972 Winter | |
| Joel Otto | United States | Ice hockey | 1998 Winter | |
| John Otto | Road cycling | 1920 Summer | |
| Kristin Otto | East Germany | Swimming | 1988 Summer | |
| Louise Otto | Germany | 1912 Summer | |
| Poul Otto | Denmark | Athletics | 1936 Summer | |
| Rudolf Otto | Germany | Art competitions | 1936 Summer | |
| Sylke Otto | Luge | 1992 Winter, 2002 Winter, 2006 Winter | |
| Werner Otto | East Germany | Track cycling | 1968 Summer, 1972 Summer | |
| Marcel Otto-Bruc | France | Shooting | 1960 Summer | |
| Margit Otto-Crépin | Equestrian dressage | 1984 Summer, 1988 Summer, 1992 Summer, 1996 Summer | |
| Sergio Ottolina | Italy | Athletics | 1964 Summer, 1968 Summer | |
| Luca Ottolino | Bobsleigh | 2006 Winter | |
| Emanuele Ottonello | Sailing | 1968 Summer | |
| Anna Ottosson | Sweden | Alpine skiing | 1998 Winter, 2002 Winter, 2006 Winter | |
| Jan Ottosson | Cross country skiing | 1984 Winter, 1988 Winter, 1992 Winter, 1994 Winter | |
| Peter Ottosson | Ice hockey | 1992 Winter | |
| Eddy Ottoz | Italy | Athletics | 1964 Summer, 1968 Summer | |
| Laurent Ottoz | 1992 Summer, 1996 Summer | |
| Idara Otu | Nigeria | 2012 Summer | |
| Beauty Otuedo [ Wikidata ] | Canoe sprint | 2024 Summer | |
| Stefan Otulakowski | Poland | Field hockey | 1972 Summer | |
| Christina Otzen | Denmark | Sailing | 2004 Summer | |
| Volmer Otzen | Diving | 1924 Summer | |
| Ou Ching-chieh | Chinese Taipei | Softball | 1996 Summer | |
| Ou Jingbai | China | 1996 Summer | |
| Ou Shaoyan | Rowing | 1996 Summer, 2000 Summer | |
| Ou Xiaotao | Freestyle skiing | 1998 Winter, 2002 Winter, 2006 Winter | |
| Ou Xuanyi | Badminton | 2024 Summer | |
| Ou Yushan | Artistic gymnastics | 2020 Summer, 2024 Summer | |
| Ou Zixia | Field hockey | 2016 Summer, 2020 Summer, 2024 Summer | |
| Mohamed Ouaadi | France | Athletics | 2000 Summer | |
| Denise Ouabangui | Central African Republic | 1996 Summer | |
| Ali Ouabbou | Morocco | Boxing | 1972 Summer | |
| Hachemi Ouahchi | Tunisia | Football | 1988 Summer | |
| Ahmad Ouachit | Morocco | Alpine skiing | 1984 Winter, 1988 Winter | |
| Hamid Oujebbad | 1984 Winter | |
| Mohamed Amine Ouadahi | Algeria | Boxing | 2012 Summer | |
| Lahcen Ouadani | Morocco | Football | 1984 Summer | |
| Abdelkebir Ouaddar | Equestrian jumping | 2016 Summer, 2020 Summer | |
| Chokri El Ouaer | Tunisia | Football | 1996 Summer | |
| Joseph-Dieudonné Ouagon | Central African Republic | Basketball | 1988 Summer | |
| Lamine Ouahab | Algeria | Tennis | 2004 Summer | |
| Manon Ouaiss [ Wikidata ] | Lebanon | Alpine skiing | 2022 Winter | |
| Abdelkrim Ouakali | Algeria | Wrestling | 2024 Summer | |
| Salima El Ouali Alami | Morocco | Athletics | 2012 Summer, 2016 Summer | |
| Fatiha Ouali | France | 2000 Summer | |
| Bibiano Ouano | Philippines | Basketball | 1936 Summer | |
| Muncef Ouardi | Canada | Speed skating | 2014 Winter | |
| Zouhair El-Ouardi | Morocco | Athletics | 2004 Summer | |
| Samira Ouass | Weightlifting | 2016 Summer | |
| Newfel Ouatah | Algeria | Boxing | 2008 Summer | |
| Mahdi Ouatine | Morocco | 2008 Summer | |
| Zié Ouattara | Ivory Coast | Football | 2020 Summer | |
| Seloua Ouaziz | Morocco | Athletics | 2000 Summer | |
| Zahra Ouaziz | 1996 Summer | |
| Nordine Oubaali | France | Boxing | 2008 Summer, 2012 Summer | |
| Mohamed Oubahim | Morocco | Cross country skiing | 1992 Winter | |
| Yamna Oubouhou | France | Athletics | 2000 Summer | |
| Mahjouba Oubtil | Morocco | Boxing | 2012 Summer | |
| Ludovic Oucéni | France | Athletics | 2020 Summer | |
| Hassan Oucheikh | Morocco | Boxing | 2000 Summer | |
| Ai Ouchi | Japan | Archery | 1996 Summer | |
| Masushi Ouchi | Weightlifting | 1964 Summer, 1968 Summer | |
| Kamel Ouchia | Algeria | Handball | 1984 Summer, 1988 Summer | |
| El Houssaine Ouchla | Morocco | Football | 2000 Summer | |
| Sam Oud | Netherlands | Canoe slalom | 2004 Summer | |
| Willy den Ouden | Swimming | 1932 Summer, 1936 Summer | |
| Jaap Oudkerk | Track cycling | 1960 Summer, 1964 Summer | |
| Chaleunsouk Oudomphanh | Laos | Athletics | 2004 Summer | |
| Aad Oudt | Netherlands | Swimming | 1964 Summer, 1968 Summer | |
| Bilel Ouechtati | Tunisia | Wrestling | 2012 Summer | |
| Adama Ouedraogo | Burkina Faso | Swimming | 2012 Summer, 2020 Summer | |
| Angelika Ouedraogo | 2012 Summer, 2016 Summer, 2020 Summer | |
| Élodie Ouédraogo | Belgium | Athletics | 2004 Summer, 2008 Summer, 2012 Summer | |
| Julien Ouedraogo | Burkina Faso | Fencing | 2008 Summer | |
| Mamadou Ouedraogo | Swimming | 2004 Summer | |
| Robert Ouellet | France | Ice hockey | 1998 Winter | |
| Ronald Ouellet | Canada | Wrestling | 1972 Summer | |
| Caroline Ouellette | Ice hockey | 2002 Winter, 2006 Winter, 2010 Winter, 2014 Winter | |
| Gerald Ouellette | Shooting | 1956 Summer, 1968 Summer | |
| Hanatou Ouelogo | Burkina Faso | Judo | 2004 Summer, 2008 Summer | |
| Rachida Ouerdane | Algeria | 2004 Summer, 2008 Summer | |
| Oussama Oueslati | Tunisia | Taekwondo | 2016 Summer | |
| Wayne Ough | Australia | Baseball | 2004 Summer | |
| Carolyne Oughton | Canada | Alpine skiing | 1972 Winter | |
| Fabrice Ougier | France | Freestyle skiing | 1998 Winter | |
| Mélanie Ougier | Luge | 2002 Winter | |
| Hanane Ouhaddou | Morocco | Athletics | 2008 Summer | |
| Aziz Ouhadi | 2012 Summer, 2016 Summer | |
| Azzedine Ouhib | Algeria | Handball | 1984 Summer | |
| Balkissa Ouhoumoudou | Niger | Swimming | 2000 Summer | |
| Mariama Ouiminga | Burkina Faso | Athletics | 1988 Summer | |
| Salifou Koucka Ouiminga | Judo | 2000 Summer | |
| Ibrahim Mohamed Al-Ouiran | Saudi Arabia | Athletics | 1988 Summer | |
| Mimoun Ouitot | Morocco | Alpine skiing | 1968 Winter | |
| Ouk Chanthan | Cambodia | Athletics | 1996 Summer, 2000 Summer | |
| Larbi Oukada | Morocco | 1968 Summer | |
| Fatima-Zohra Oukazi | Algeria | Volleyball | 2008 Summer | |
| Abdessamad Oukhelfen | Spain | Athletics | 2024 Summer | |
| Robert Ouko | Kenya | 1968 Summer, 1972 Summer | |
| Charles Oula | Monaco | Bobsleigh | 2002 Winter | |
| Gaston Oula | Ivory Coast | Judo | 1984 Summer | |
| Abdulnasser El-Oulabi | Syria | Wrestling | 1980 Summer | |
| Mohamed El-Oulabi | 1980 Summer | |
| Farid Oulami | Algeria | Table tennis | 2000 Summer | |
| Naby Oularé [ Wikidata ] | Guinea | Football | 2024 Summer | |
| Mohamed Ould Khalifa | Mauritania | Athletics | 1988 Summer, 1992 Summer | |
| Noureddine Ould Ménira | 1992 Summer, 1996 Summer | |
| Johnny Ould | Great Britain | Boxing | 1960 Summer | |
| Lenka Oulehlová | Czechoslovakia, Czech Republic | Rhythmic gymnastics | 1988 Summer, 1992 Summer, 1996 Summer | |
| Abdelmajid Oulmers | Morocco | Football | 2000 Summer | |
| Lydia Oulmou | Algeria | Volleyball | 2008 Summer, 2012 Summer | |
| Matthias Ouma | Uganda | Boxing | 1968 Summer, 1972 Summer | |
| Sanda Bouba Oumarou | Central African Republic | Basketball | 1988 Summer | |
| Méryem Oumezdi | Morocco | Athletics | 1988 Summer | |
| Sofiane Oumiha | France | Boxing | 2016 Summer, 2020 Summer, 2024 Summer | |
| Oun Yao-ling | Chinese Taipei | Weightlifting | 1964 Summer | |
| Haig Oundjian | Great Britain | Figure skating | 1968 Winter, 1972 Winter | |
| Alex Oundo | Kenya | Boxing | 1964 Summer | |
| Terrence Oung | Myanmar | 1956 Summer | |
| Sikhounxay Ounkhamphanyavong | Laos | Swimming | 2000 Summer | |
| Chantal Ouoba | Burkina Faso | Athletics | 1996 Summer | |
| Souneat Ouphaphone | Laos | Boxing | 1980 Summer | |
| Asami Oura | Japan | Water polo | 1984 Summer | |
| Masafumi Ōura | Volleyball | 1992 Summer | |
| Foued Ourabi | Tunisia | Sailing | 2004 Summer | |
| Abdelhalim Ouradi | Algeria | Boxing | 2008 Summer | |
| Sarah Ourahmoune | France | 2016 Summer | |
| Azzeddine Ourahou | Morocco | Football | 2004 Summer | |
| Vlastimil Ouředník | Czechoslovakia | Canoe slalom | 1972 Summer | |
| Hanene Ourfelli | Tunisia | Weightlifting | 2008 Summer | |
| Dan Ouseley | Great Britain | Rowing | 2004 Summer | |
| Rajiv Ouseph | Badminton | 2012 Summer, 2016 Summer | |
| Kai Outa | Finland | Weightlifting | 1952 Summer | |
| Mouhcine Outalha | Morocco | Athletics | 2024 Summer | |
| Willets Outerbridge | United States | Sailing | 1928 Summer | |
| Luiz Outerelo | Brazil | Diving | 2016 Summer | |
| Serguei Outschakov | Ukraine | Road cycling | 1996 Summer, 2000 Summer | |
| Nathan Outteridge | Australia | Sailing | 2008 Summer, 2012 Summer, 2016 Summer | |
| Eliza Outtrim | United States | Freestyle skiing | 2014 Winter | |
| Cristina Ouviña | Spain | Basketball | 2020 Summer | |
| Olavi Ouvinen | Finland | Boxing | 1948 Summer | |
| Hazel Ouwehand | New Zealand | Swimming | 2024 Summer | |
| Ouyang Kunpeng | China | 2000 Summer, 2004 Summer | |
| Sara Ouzande [ Wikidata ] | Spain | Canoe sprint | 2024 Summer | |
| Tigran Ouzlian | Greece | Boxing | 1996 Summer, 2000 Summer | |
| Kalliopi Ouzouni | Athletics | 2000 Summer, 2004 Summer | |
| Éva Óvári | Hungary | Artistic gymnastics | 1976 Summer, 1980 Summer | |
| Eszter Óváry | 1988 Summer, 1996 Summer | |
| László Óváry | Wrestling | 1992 Summer | |
| Toivo Ovaska | Finland | Speed skating | 1928 Winter | |
| Juha Ovaskainen | Diving | 1984 Summer, 1988 Summer | |
| Vladislava Ovcharenko | Tajikistan | Athletics | 2012 Summer | |
| Lyubov Ovcharova | Russian Olympic Committee | Wrestling | 2020 Summer | |
| Vladimir Ovchinnikov | Soviet Union, Russia | Athletics | 1988 Summer, 1996 Summer, 2000 Summer | |
| Yuri Ovchinnikov | Soviet Union | Figure skating | 1972 Winter, 1976 Winter | |
| Evgeniya Ovchinnikova | Russia | Equestrian eventing | 2016 Summer | |
| Kristina Ovchinnikova | Kazakhstan | Athletics | 2020 Summer | |
| Mariya Ovchinnikova | 2020 Summer | |
| Oksana Ovchinnikova | Russia | 1996 Summer | |
| Yelena Ovchinnikova | Artistic swimming | 2008 Summer | |
| Konstantīns Ovčiņņikovs | Latvia | Judo | 2012 Summer | |
| Alexander Ovechkin | Russia | Ice hockey | 2006 Winter, 2010 Winter, 2014 Winter | |
| Nadezhda Ovechkina | Soviet Union | Field hockey | 1980 Summer | |
| Tatyana Ovechkina | Basketball | 1976 Summer, 1980 Summer | |
| Dmitry Ovechko | Russia | Rowing | 2000 Summer | |
| Mette Ove-Petersen | Denmark | Swimming | 1952 Summer | |
| Het Lichtet Overal [ Wikidata ] | Belgium | Art competitions | 1928 Summer | |
| Scott Overall | Great Britain | Athletics | 2012 Summer | |
| Carla Overbeck | United States | Football | 1996 Summer | |
| Håkon Øverby | Norway | Wrestling | 1968 Summer, 1972 Summer | |
| Petter Øverby | Handball | 2020 Summer, 2024 Summer | |
| Sigurd Overby | United States | Cross country skiing, Nordic combined | 1924 Winter | |
| Marie Overbye | Denmark | Triathlon | 2000 Summer | |
| Mirjam Overdam | Netherlands | Water polo | 2000 Summer | |
| Gerard Overdijkink | Field hockey | 1960 Summer | |
| Tom Overend | Canada | Speed skating | 1976 Winter | |
| Katia Overfeldt | Belgium | Artistic swimming | 1984 Summer | |
| Knud Børge Overgaard | Denmark | Football | 1948 Summer | |
| Elling Øvergård | Norway | Shooting | 1968 Summer | |
| Emily Overholt | Canada | Swimming | 2016 Summer | |
| Amanda Overland | Short track speed skating | 2006 Winter | |
| Cindy Overland | Speed skating | 1998 Winter, 2002 Winter | |
| Jon Terje Øverland | Norway | Alpine skiing | 1964 Winter, 1968 Winter | |
| Kevin Overland | Canada | Speed skating | 1998 Winter | |
| Jarmo Övermark | Finland | Wrestling | 1976 Summer, 1980 Summer, 1984 Summer | |
| Kari Övermark | 1976 Summer | |
| Puck Oversloot | Netherlands | Swimming | 1932 Summer | |
| David Overton | Canada | Rowing | 1964 Summer | |
| Elli Overton | Australia | Swimming | 1992 Summer, 1996 Summer, 2000 Summer | |
| Whitey Overton | United States | Athletics | 1948 Summer | |
| Friedel Overwien | Germany | Artistic gymnastics | 1952 Summer | |
| Nick Ovett | Great Britain | Luge | 1988 Winter, 1992 Winter | |
| Steve Ovett | Athletics | 1976 Summer, 1980 Summer, 1984 Summer | |
| Heiner Oviedo | Costa Rica | Taekwondo | 2012 Summer | |
| Luis Oviedo | Cuba | Volleyball | 1980 Summer | |
| Roberto Oviedo | Argentina | Boxing | 1984 Summer | |
| Raymond Ovinou | Papua New Guinea | Judo | 2012 Summer, 2016 Summer | |
| Régis Ovion | France | Road cycling | 1972 Summer | |
| Badie Ovnteni | Niger | Boxing | 1988 Summer | |
| Didier Ovono | Gabon | Football | 2012 Summer | |
| Tore Øvrebø | Norway | Rowing | 1988 Summer | |
| Aleksandr Ovsyankin | Soviet Union | Fencing | 1956 Summer | |
| Oleg Ovsyannikov | Russia | Figure skating | 1998 Winter | |
| Dimitrij Ovtcharov | Germany | Table tennis | 2008 Summer, 2012 Summer, 2016 Summer, 2020 Summer, 2024 Summer | |
| Olya Ovtchinnikova | Canada | Fencing | 2008 Summer | |