Aruba sent a delegation to compete at the 2004 Summer Olympics in Athens, Greece from 13 to 29 August 2004. The delegation's participation in the Athens Olympics marked Aruba's fifth appearance at the Summer Olympics since the Dutch colony's debut at the 1988 Summer Olympics in Seoul, South Korea. Four athletes competed across three sports. None of the track or swimming athletes advanced past the first round in their events, and as of Athens, no Arubans had medaled in any events. Roshendra Vrolijk bore Aruba's flag at the ceremonies.
Michael George Klim, OAM is a Polish-born Australian swimmer, Olympic gold medallist, world champion, and former world record-holder of the 1990s and 2000s. He is known as the creator of straight arm freestyle.
Rimvydas Šalčius is a Lithuanian former swimmer, who specialized in butterfly events. He is a multiple-time Lithuanian champion, and a two-time national record holder in both the men's butterfly and medley relay events. He also set a junior record time of 53.25 seconds by winning the gold medal in the men's 100 m butterfly at the 2003 European Championships in Glasgow, Scotland.
Sotirios Pastras is a Greek former swimmer, who specialized in butterfly events. He is a multiple-time Greek champion and record holder in the butterfly. Pastras is a computer engineering graduate at University of Thessaly, and is currently a member of Nova Club in Volos, under the tutelage of his personal coach Nikolaos Prantzos.
Daniel William Henry "Danny" Wong Bego, OLY is a Malaysian swimmer, who specialises in freestyle and butterfly events. He emerged as one of Malaysia's most promising and outstanding swimmers, winning a total of fifteen medals at the Southeast Asian Games, and breaking six national records. He was the first Malaysian swimmer to compete in three different events at a single Olympic Games.
Donny Budiarto Utomo is an Indonesian swimmer, who specialized in butterfly events. He is a former multiple-time national record holder for the men's butterfly, and a six-time medalist at the Southeast Asian Games. He is also a two-time defending champion for the 200 m butterfly, before losing out to Malaysia's Daniel Bego at the 2007 Southeast Asian Games in Bangkok, Thailand.
Eduardo Germán Otero is an Argentine former swimmer, who specialized in backstroke and butterfly events. He is a three-time Olympian, a multiple-time national record holder, and a two-time champion for the 50 m backstroke at the South American Games. He is also a member of Club Nadadores del Rio Plata, and is coached and trained by Marcelo "Yuri" Quaglia.
Ravil Nachaev is an Uzbek former swimmer, who specialized in sprint freestyle and butterfly events. He is a three-time Olympian, and a gold medalist in the 50 m freestyle at the 2002 Asian Games in Busan, South Korea.
Michal Rubáček is a Czech swimmer, who specialized in butterfly events. He is a two-time Olympian, and a multiple-time Czech national record holder for the butterfly events.
Jeong Doo-hee is a South Korean former swimmer, who specialized in butterfly events. He represented his nation South Korea at the 2004 Summer Olympics, and shared silver medals with Park Seon-kwan, Choi Kyu-woong, and Park Tae-hwan in the 4×100 m medley relay at the 2010 Asian Games in Guangzhou, China.
Juan Pablo Valdivieso is a Peruvian former swimmer, who specialized in butterfly events. Valdivieso holds a dual citizenship between his parents' nation Peru and the United States, where he currently resides. He is also influenced by his grandfather Juan Valdivieso, who played for Peru's soccer team at the 1936 Summer Olympics in Berlin.
Pavel Mikalayevich Lahun is a Belarusian former swimmer, who specialized in freestyle and butterfly events. He is a two-time Olympian, and a three-time medalist at the FINA World Cup.
Eugene Botes is a South African former swimmer, who specialized in butterfly events. He became the first swimmer to represent his country South Africa in international tournaments, while playing for the Penn State Nittany Lions in his senior season. He also holds a dual citizenship between South Africa and the United States.
Daniel O'Keeffe is a Guamanian former swimmer, who specialized in butterfly events. He is a two-time Olympian, and currently holds a Guamanian record in the 100-meter butterfly (55.05).
Aghiles Slimani is an Algerian former swimmer, who specialized in butterfly events. Slimani qualified for two swimming events at the 2004 Summer Olympics in Athens, by posting FINA B-standard entry times of 55.40 and 2:03.18 from the World Championships in Barcelona, Spain. In the 200 m butterfly, Slimani challenged seven other swimmers in heat two, including Olympic veteran Vladan Marković of Serbia. He raced to sixth place and thirty-first overall by 0.16 of a second behind Markovic in 2:04.93. In his second event, 100 m butterfly, Slimani placed forty-eighth on the morning's preliminaries. Swimming in heat three, he edged out Turkey's Onur Uras to take a seventh seed by fifteen hundredths of a second (0.15) in 56.22.
Oleg Lyashko is an Uzbek former swimmer, who specialized in butterfly events. Lyashko qualified for the men's 100 m butterfly at the 2004 Summer Olympics in Athens, by posting a FINA B-standard of 56.08 from the Kazakhstan Open Championships in Almaty. He challenged seven other swimmers in heat two, including 17-year-old Michal Rubáček of the Czech Republic. He raced to second place by a 1.03-second margin behind winner Rubacek in a personal best of 55.90. Lyashko failed to advance into the semifinals, as he placed forty-sixth overall in the preliminaries.
Albert Christiadi Sutanto is an Indonesian former swimmer, who specialized in butterfly and medley events. He is a two-time Olympian, and multi medalist 9 Gold 5 Silver and 16 Bronze at the Southeast Asian Games.
Josef Horký is a Czech former swimmer, who specialized in freestyle, butterfly, and individual medley events. He is a two-time Olympian, a semifinalist in the 200 m butterfly at the European Championships (2002), and a member of Kometa Brno under his head coach Ondřej Butir.
Richard Sam Bera is a former Indonesian swimmer, who specialized in sprint and middle-distance freestyle events. He is a three-time Olympian, a bronze medalist at the Asian Games (1990), and a twenty-three times SEA Games gold-medalist since his debut in 1987. He is regarded as Indonesia's most successful swimmer in the sporting history. Up until 2015, Bera held several Indonesian and Southeast Asian Games records in sprint freestyle events from the Southeast Asian Games.
Anthony Ang Kang Keam is a Malaysian former swimmer, who specialised in butterfly events. He is a two-time Olympian, a double SEA Games titleholder in a butterfly double, a Bolles School graduate, and a member of Florida State University (1998-1999) and University of Minnesota (2000-2002) swimming and diving team while studying in the United States.
Indonesia 
