| Name | Nation | Sport | Games | Notes |
|---|
| 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 | Hungary | 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 | 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 | |
| Ow Soon Kooi | Malaysia | Field hockey | 1976 Summer, 1984 Summer | |
| Tomoko Owada | Japan | Fencing | 1964 Summer | |
| Khamis Al-Owairan | Saudi Arabia | Football | 1996 Summer | |
| Bogusław Owczarek | Poland | Equestrian eventing | 1996 Summer | |
| Eddie Owen | Great Britain | Athletics | 1908 Summer, 1912 Summer | |
| Edwyn Owen | United States | Ice hockey | 1960 Winter | |
| Ellen Owen | Diving | 1992 Summer | |
| George Owen | Great Britain | Track cycling | 1924 Summer | |
| Ieuan Owen | Weightlifting | 1972 Summer | |
| Jon Owen | United States | Luge | 1988 Winter | |
| Laurence Owen | Figure skating | 1960 Winter | |
| Maribel Owen | 1960 Winter | |
| Nancy Owen | Volleyball | 1964 Summer, 1968 Summer | |
| Rada Owen | Swimming | 2000 Summer | |
| Rod Owen-Jones | Australia | Water polo | 2000 Summer | |
| Ger Owens | Ireland | Sailing | 2004 Summer, 2008 Summer, 2012 Summer | |
| James Owens | United States | Athletics | 1976 Summer | |
| Jenny Owens | Australia | Alpine skiing, Freestyle skiing | 2002 Winter, 2010 Winter, 2014 Winter | |
| Jesse Owens | United States | Athletics | 1936 Summer | |
| Kai Owens | Freestyle skiing | 2022 Winter | |
| Ryan Owens | Great Britain | Track cycling | 2020 Summer | |
| Tarja Owens | Ireland | Cycling mountain bike | 2000 Summer | |
| Thomas Owens | Australia | Sailing | 1964 Summer | |
| Ayden Owens-Delerme | Puerto Rico | Athletics | 2024 Summer | |
| Alison Owen-Spencer | United States | Cross country skiing | 1972 Winter, 1980 Winter | |
| Öwez Öwezow | Turkmenistan | Weightlifting | 2020 Summer | |
| Pamella Owino [ Wikidata ] | Kenya | Volleyball | 2024 Summer | |
| Victor Owino | Field hockey | 1988 Summer | |
| Dodovic Owiny | Uganda | Boxing | 1984 Summer | |
| Esraa Owis | Egypt | Athletics | 2024 Summer | |
| Charles Owiso | Kenya | Boxing | 1984 Summer | |
| John Owiti | Athletics | 1964 Summer | |
| Own Kongding | China | Weightlifting | 1936 Summer | |
| Atisi Owoh | Nigeria | Table tennis | 2000 Summer | |
| Felix Owolabi | Football | 1980 Summer | |
| Kubrat Owolabi | Table tennis | 1988 Summer | |
| Nicolas Owona | Cameroon | Road cycling | 1972 Summer, 1976 Summer, 1980 Summer | |
| James Owoo | Ghana | Athletics | 1952 Summer | |
| Paskar Owor | Uganda | 2000 Summer, 2004 Summer | |
| Lily Owsley | Great Britain | Field hockey | 2016 Summer, 2020 Summer, 2024 Summer | |
| George Owu | Ghana | Football | 2004 Summer | |
| Aaron Ghebre Owusu | Eritrea | Swimming | 2024 Summer | |
| Andrew Owusu | Ghana | Athletics | 1996 Summer, 2000 Summer, 2004 Summer | |
| Edward Owusu | 1968 Summer | |
| Frederick Owusu | 1960 Summer | |
| John Owusu | 1952 Summer | |
| Joshua Owusu | 1972 Summer | |
| Kwasi Owusu | Football | 1972 Summer | |
| Flings Owusu-Agyapong | Athletics | 2016 Summer | |
| Noel Oxenbury | Canada | Swimming | 1936 Summer | |
| Johan Gabriel Oxenstierna | Sweden | Modern pentathlon | 1932 Summer | |
| Tom Erik Oxholm | Norway | Speed skating | 1980 Winter | |
| John Oxley | United States | Athletics | 1904 Summer | |
| Johnny Oxley | Great Britain | Ice hockey | 1948 Winter | |
| Tanya Oxley | Barbados | Athletics | 2000 Summer | |
| Juan Carlos Oxoby | Argentina | Shooting | 1964 Summer | |
| Chris Oxspring | Australia | Baseball | 2004 Summer | |
| Mette Oxvang | Denmark | Athletics | 1960 Summer | |
| Masaki Oya | Japan | 1996 Summer | |
| Chihiro Oyagi | Artistic gymnastics | 1984 Summer | |
| Masaaki Oyagi | Luge | 1976 Winter | |
| Yoshi Oyakawa | United States | Swimming | 1952 Summer, 1956 Summer | |
| Kana Oyama | Japan | Volleyball | 2004 Summer | |
| Mikio Oyama | Speed skating | 1976 Winter | |
| Shiho Oyama | Golf | 2016 Summer | |
| Taeko Oyama | Basketball | 1996 Summer, 2004 Summer | |
| Jesús Oyarbide | Spain | Athletics | 1928 Summer | |
| José Ramón Oyarzábal | Rowing | 1980 Summer, 1984 Summer, 1988 Summer | |
| Mikel Oyarzabal | Football | 2020 Summer | |
| Timon Oyebami | Nigeria | Athletics | 1968 Summer, 1972 Summer | |
| Olumide Oyedeji | Basketball | 2012 Summer | |
| Samson Oyeledun | Athletics | 1980 Summer, 1984 Summer | |
| Anais Oyembo | Gabon | 2000 Summer | |
| Cornelius van Oyen | Germany | Shooting | 1936 Summer | |
| Abi Oyepitan | Great Britain | Athletics | 2004 Summer, 2012 Summer | |
| Moses Oyiki | Nigeria | 1996 Summer | |
| Ivan, Viscount d'Oyley | United States | Fencing | 1900 Summer | |
| Tamara Oynick | Mexico | Swimming | 1968 Summer | |
| Tsutomu Ōyokota | Japan | 1932 Summer | |
| Nelson Oyoo | Kenya | Rugby sevens | 2020 Summer | |
| Camilyne Oyuayo | 2016 Summer | |
| Dugarsürengiin Oyuunbold | Mongolia | Wrestling | 1980 Summer | |
| Gantömöriin Oyuungerel | Swimming | 2012 Summer | |
| Sambuugiin Oyuuntsetseg | Archery | 1988 Summer | |
| Davaasürengiin Oyuuntuyaa | Artistic gymnastics | 1980 Summer | |
| George Oywello | Uganda | Boxing | 1960 Summer, 1964 Summer | |
| Yaron Oz | Israel | Football | 1976 Summer | |
| Kai Ozaki | Japan | Freestyle skiing | 2006 Winter, 2010 Winter | |
| Kōsuke Ozaki [ Wikidata ] | Biathlon | 2022 Winter | |
| Michiharu Ozaki | Shooting | 1976 Summer | |
| Nonoka Ozaki | Wrestling | 2024 Summer | |
| Seri Ozaki | Fencing | 2024 Summer | |
| Yoshimi Ozaki | Athletics | 2012 Summer | |
| Mehmet Özal | Turkey | Wrestling | 2004 Summer, 2008 Summer | |
| Hiromi Ozawa | Japan | Speed skating | 1984 Winter | |
| Junko Ozawa | Football | 1996 Summer | |
| Michihiro Ozawa | 1956 Summer | |
| Mika Ozawa | Short track speed skating | 2006 Winter, 2010 Winter | |
| Misaki Ozawa | Field hockey | 2008 Summer | |
| Sachi Ozawa | Short track speed skating | 1998 Winter | |
| Tsugeo Ozawa | Fencing | 1960 Summer | |
| Fatih Özbaş | Turkey | Wrestling | 1992 Summer | |
| Szofi Özbas | Hungary | Judo | 2020 Summer, 2024 Summer | |
| Cansu Özbay | Turkey | Volleyball | 2020 Summer, 2024 Summer | |
| Elis Özbay | Rowing | 2024 Summer | |
| Muhammed Furkan Özbek | Weightlifting | 2020 Summer, 2024 Summer | |
| Rızvan Özbey | Cross country skiing | 1968 Winter | |
| Sacit Özbey | 1976 Winter | |
| Yavuz Özbey | 1976 Winter | |
| İlham Tanui Özbilen | Athletics | 2012 Summer, 2016 Summer | |
| Janez Ožbolt | Slovenia | Biathlon | 1992 Winter, 1994 Winter, 1998 Winter, 2002 Winter, 2006 Winter | |
| Kaya Özcan | Turkey | Wrestling | 1968 Summer | |
| Mustafa Özcan | Athletics | 1948 Summer | |
| Kemal Özçelik | Equestrian eventing | 1956 Summer | |
| Serap Özçelik | Karate | 2020 Summer | |
| Kamil Özdağ | Wrestling | 1976 Summer | |
| Ali Özdemir | 1948 Summer, 1952 Summer | |
| Bayram Özdemir | 1996 Summer | |
| Ela Naz Özdemir | Swimming | 2024 Summer | |
| Kuddusi Özdemir | Wrestling | 1976 Summer | |
| Agata Ozdoba-Błach | Poland | Judo | 2020 Summer | |
| Sanja Ožegović | Yugoslavia | Basketball | 1980 Summer, 1984 Summer | |
| Tokiko Ozeki | Japan | Cross country skiing | 1972 Winter | |
| Ali Özen | Turkey | Wrestling | 2000 Summer | |
| Türker Özenbaş | Shooting | 1968 Summer | |
| Gizem Özer | Boxing | 2024 Summer | |
| Kayhan Özer | Athletics | 2020 Summer, 2024 Summer | |
| Igor Ozerov | Russia | Short track speed skating | 1994 Winter | |
| Yuri Ozerov | Soviet Union | Basketball | 1952 Summer, 1956 Summer | |
| Cēzars Ozers | 1960 Summer | |
| Kaspars Ozers | Latvia | Road cycling | 1996 Summer | |
| Hasan Kaan Özgönenç | Turkey | Sailing | 2004 Summer | |
| Fahir Özgüden | Athletics | 1960 Summer | |
| Alaattin Özgür | Wrestling | 1984 Summer | |
| Nikolay Ozhegin | Russia | Judo | 1996 Summer | |
| Alisa Ozhogina | Spain | Artistic swimming | 2020 Summer, 2024 Summer | |
| Norbert Ozimek | Poland | Weightlifting | 1968 Summer, 1972 Summer | |
| Paul Oziol de Pignol | France | Fencing | 1928 Summer | |
| Ibo Oziti | Nigeria | Wrestling | 1992 Summer, 1996 Summer, 2000 Summer | |
| Joe Oziti | 1992 Summer | |
| Ertan Özkan | Turkey | Athletics | 2020 Summer | |
| Ertuğrul Özkan | Sailing | 1984 Summer | |
| Hüseyin Özkan | Judo | 2000 Summer | |
| Kerem Özkan [ Wikidata ] | Sailing | 1996 Summer | |
| Sibel Özkan | Weightlifting | 2008 Summer | |
| Naci Özkaya | Football | 1948 Summer | |
| Peri Suzan Özkum | Diving | 1976 Summer | |
| Ekke Ozlberger | Austria | Art competitions | 1936 Summer, 1948 Summer | |
| Bekir Özlü | Georgia, Turkey | Judo | 2012 Summer, 2016 Summer | |
| Józef Oźmin | Poland | Art competitions | 1936 Summer | |
| Stanisław Ożóg | Athletics | 1960 Summer | |
| Edvin Ozolin | Soviet Union | 1960 Summer, 1964 Summer | |
| Agnese Ozoliņa | Latvia | Swimming | 1996 Summer, 2000 Summer, 2004 Summer | |
| Elvīra Ozoliņa | Soviet Union | Athletics | 1960 Summer, 1964 Summer | |
| Sanita Ozoliņa | Latvia | Rowing | 1996 Summer | |
| Sinta Ozoliņa-Kovala | Athletics | 2008 Summer, 2012 Summer, 2016 Summer | |
| Rein Ozoline | Australia | Wrestling | 1996 Summer, 2000 Summer | |
| Alberts Ozoliņš | Latvia | Weightlifting | 1924 Summer | |
| Anna Ozolins | Australia | Rowing | 1996 Summer | |
| Sandis Ozoliņš | Latvia | Ice hockey | 2002 Winter, 2006 Winter, 2014 Winter | |
| Dainis Ozols | Road cycling | 1992 Summer, 1996 Summer, 2000 Summer | |
| Jānis Ozols | Bobsleigh | 1998 Winter, 2002 Winter, 2006 Winter | |
| Patriks Ozols [ Wikidata ] | Ice hockey | 2022 Winter | |
| Roberts Ozols | Track cycling | 1928 Summer | |
| Arvīds Ozols-Bernē [ Wikidata ] | Russia | Athletics | 1912 Summer | |
| Abuaihuda Ozon | Syria | Weightlifting | 1984 Summer | |
| Titus Ozon | Romania | Football | 1952 Summer | |
| Petar Ozretić | Yugoslavia | Rowing | 1948 Summer | |
| Neriman Özsoy | Turkey | Volleyball | 2012 Summer | |
| András Ozsvár | Hungary | Judo | 1980 Summer | |
| Lale Öztürk | Turkey | Athletics | 2004 Summer | |
| Remzi Öztürk | Wrestling | 1992 Summer | |
| Sebahattin Öztürk | 1992 Summer, 1996 Summer | |
| Yusuf Öztürk | Boxing | 1996 Summer | |
| Zeki Öztürk | Athletics | 1988 Summer, 1992 Summer | |
| Tacettin Öztürkmen | Track cycling | 1928 Summer | |
| İhsan Sabri Özün | Swimming | 1984 Summer | |
| Kemal Sadri Özün | 1984 Summer | |
| Çiğdem Özyaman | Shooting | 2012 Summer | |
| Ahmet Suat Özyazıcı | Football | 1960 Summer | |
| İlke Özyüksel | Modern pentathlon | 2016 Summer, 2020 Summer, 2024 Summer | |