Portugal competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Portuguese athletes have competed at every Summer Olympic Games in the modern era since 1912. The Olympic Committee of Portugal sent the nation's second-largest team to the Games. A total of 81 athletes, 64 men and 17 women, were selected by the committee to participate in 15 sports. Men's football was the only team-based sport in which Portugal had its representation at these Games. There was only a single competitor in badminton, canoeing, equestrian, artistic and trampoline gymnastics, triathlon, and wrestling, which made its official Olympic comeback after an eight-year absence.
Kazakhstan competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's third appearance at the Summer Olympics in the post-Soviet era.
Ukraine competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's third consecutive appearance at the Summer Olympics in the post-Soviet era. The National Olympic Committee of Ukraine sent the nation's largest ever delegation to these Games. A total of 240 athletes, 125 men and 115 women, took part in 21 sports. Women's handball was the only team-based sport in which Ukraine had its representation at these Games for the first time. There was only a single competitor in modern pentathlon and taekwondo.
Malaysia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's twelfth appearance at the Olympics, although it had previously competed in two other games under the name Malaya. Malaysia, however, did not participate at the 1980 Summer Olympics in Moscow, because of its partial support to the United States boycott.
The Philippines competed at the 2004 Summer Olympics in Athens, from 13 to 29 August 2004. This was the nation's eighteenth appearance at the Olympics, except the 1980 Summer Olympics in Moscow because of its partial support to the United States boycott.
Hong Kong competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. It was the territory's thirteenth appearance at the Olympics and, at the opening ceremony, its team was the last to enter the stadium before the host nation because of the use of the Greek alphabet.
Czech Republic competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's third appearance at the Summer Olympics after gaining its independence from the former Czechoslovakia. The Czech Olympic Committee sent the nation's largest team to the Games since the post-Czechoslovak era. A total of 142 athletes, 80 men and 62 women, competed in 19 sports; the nation's team size was roughly denser from Sydney by one sixth of the athletes. Women's basketball was the only team-based sport in which the Czech Republic had its representation at these Olympic Games. There was only a single competitor in equestrian, artistic and trampoline gymnastics, judo, and weightlifting.
Guatemala competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's eleventh appearance at the Summer Olympics, excluding three occasions after its national debut at the 1952 Summer Olympics in Helsinki.
Colombia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's sixteenth appearance at the Olympics, except the 1952 Summer Olympics in Helsinki.
Latvia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's eighth appearance at the Summer Olympics.
Kyrgyzstan competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's third appearance at the Olympics in the post-Soviet era.
Barbados competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This nation marked its ninth appearance at the Olympics, except the 1980 Summer Olympics in Moscow because of the United States boycott.
Zimbabwe competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's seventh consecutive appearance at the Olympics, after gaining its independence from the former Rhodesia.
Uruguay competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's eighteenth appearance at the Olympics, except the 1980 Summer Olympics in Moscow, because of its full support to the United States boycott.
Senegal competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's eleventh appearance at the Olympics.
Panama competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's fourteenth appearance at the Olympics since its debut in 1920. Panama did not compete on four occasions, including the 1980 Summer Olympics in Moscow, because of its partial support of the United States boycott.
Moldova competed at the 2004 Summer Olympics in Athens, from 13 to 29 August 2004. This was the nation's third consecutive appearance at the Summer Olympics in the post-Soviet era.
Iceland competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Icelandic athletes have competed at every Summer Olympic Games in the modern era since 1912, except for four occasions.
Luxembourg competed at the 2016 Summer Olympics in Rio de Janeiro, Brazil, from 5 to 21 August 2016. Since the nation's official debut in 1900, Luxembourgish athletes have appeared in every edition of the Summer Olympic Games throughout the modern era, with the exception of the sparsely attended 1904 and 1908 Summer Olympics, and the 1932 Summer Olympics in Los Angeles at the period of the worldwide Great Depression.
Luxembourg competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. Since the nation's official debut in 1900, Luxembourg athletes have appeared in every edition of the Summer Olympic Games, with the exception of the 1904 and 1908 Summer Olympics, and the 1932 Summer Olympics in Los Angeles at the period of the worldwide Great Depression.
