Algeria competed at the 2004 Summer Olympics in Athens, Greece from 13 to 29 August 2004. It first competed in the Olympics in 1964, and entered the 2004 Athens Games having won a total of twelve medals — including one gold, one silver, and three bronze medals at the 2000 Summer Olympics. These medals were in athletics and boxing. 61 competitors, 46 men and 15 women, took part in 57 events in 10 sports.
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.
Cuba competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's seventeenth appearance in the Olympics, except for some editions. Cuban athletes did not attend in two Olympic Games, where they joined the Soviet and North Korean boycott. Cuban Olympic Committee sent the nation's smallest delegation to the Games since 1972. A total of 151 athletes, 97 men and 54 women, competed in 18 sports.
Belarus competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's fifth appearance at the Summer Olympics in the post-Soviet era. The Belarus Olympic Committee sent a total of 151 athletes to the Games, 82 men and 69 women, to compete in 22 sports.
Chile competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004.
Austria competed at the 2004 Summer Olympics in Athens, Greece from 13 to 29 August 2004. 74 competitors, 54 men and 20 women, took part in 56 events in 18 sports.
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.
Switzerland competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Swiss athletes competed at every Summer Olympic Games in the modern era, except when they boycotted the 1956 Summer Olympics in Melbourne as a protest to the Soviet invasion of Hungary. The Swiss Olympic Association sent a total of 98 athletes to the Games, 59 men and 39 women, to compete in 18 sports.
Lithuania competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's sixth appearance at the Summer Olympics. The National Olympic Committee of Lithuania sent the nation's smallest delegation to the Games since the 1992 Summer Olympics in Barcelona. A total of 59 athletes, 47 men and 12 women, competed in 13 sports, including the men's basketball team as the nation's team-based sport.
Belgium competed at the 2012 Summer Olympics in London, United Kingdom, from 27 July to 12 August 2012. The Belgian Olympic Committee sent the nation's largest delegation to the Games since 1976. A total of 119 athletes, 75 men and 44 women, competed in 16 sports. There was only a single competitor in slalom canoeing, BMX cycling, equestrian dressage, rowing, shooting, table tennis, and weightlifting. Field hockey was the only team event in which Belgium was represented at these Olympic games.
Poland competed at the 2012 Summer Olympics in London, from 27 July to 12 August 2012. This was the nation's twentieth appearance at the Summer Olympics, having missed the 1984 Summer Olympics in Los Angeles because of the Soviet boycott. The Polish Olympic Committee sent a total of 218 athletes to the Games, 130 men and 88 women, to compete in 22 sports.
Argentina competed at the 2012 Summer Olympics in London, United Kingdom, from 27 July to 12 August 2012. This was the nation's twenty-third appearance at the Summer Olympic Games, having missed only three editions: the 1904 Summer Olympics in St. Louis, the 1912 Summer Olympics in Stockholm, and the 1980 Summer Olympics in Moscow, because of its support for the United States-led boycott.
Paraguay competed at the 2012 Summer Olympics in London, from 27 July to 12 August 2012. This was the nation's eleventh appearance at the Olympics, except the 1980 Summer Olympics in Moscow because of its partial support to the United States boycott.
Cuba competed at the 2012 Summer Olympics in London, from 27 July to 12 August 2012. This was the nation's nineteenth appearance in the Olympics. With baseball's removal from the Olympic program and the absence of the nation's volleyball team for the first time, the Cuban Olympic Committee sent the nation's smallest delegation to the Games since 1964. A total of 111 athletes, 66 men and 45 women, competed in 13 sports. There was only a single competitor in archery and table tennis.
Chinese Taipei competed at the 2012 Summer Olympics in London, from 27 July to 12 August 2012. "Chinese Taipei" was the designated name used by Taiwan to participate in some international organizations and almost all sporting events, including the Olympic Games. Neither the common name "Taiwan" nor the official name "Republic of China" would be used due primarily to opposition from the People's Republic of China. This was the nation's eighth consecutive appearance at the Olympics.
Greece competed at the 2012 Summer Olympics in London, United Kingdom, from 27 July to 12 August 2012. The Hellenic Olympic Committee sent a total of 103 athletes to the Games in London, 65 men and 38 women, to compete in 19 sports. Men's water polo was the only team event in which Greece was represented at these Olympic Games.
Denmark competed at the 2012 Summer Olympics in London, from 27 July to 12 August 2012. The National Olympic Committee and Sports Confederation of Denmark sent the nation's second largest delegation to the Games after the 1996 Summer Olympics in Atlanta. A total of 113 athletes, 63 men and 50 women, competed in 17 sports, although two additional athletes played as team reserves. Handball was the only team-based sport in which Denmark was represented in at these Olympic games.
Romania competed at the 2012 Summer Olympics in London from 27 July to 12 August 2012. This nation has competed at the Summer Olympic Games since its official debut in 1924, missing only two editions, including the 1948 Summer Olympics. Despite being London's third Olympic Games, this is the first time the Romanian team has competed in London. The Romanian Olympic and Sports Committee sent a total of 103 athletes to the Games, 54 men and 49 women, to compete in 14 sports.
Algeria competed at the 2012 Summer Olympics in London, United Kingdom, from 27 July to 12 August 2012. This was the nation's twelfth consecutive appearance at the Summer Olympics, except for the 1976 Summer Olympics in Montreal because of the African boycott.
Tunisia competed at the 2012 Summer Olympics in London, from 27 July to 12 August 2012. This was the nation's thirteenth appearance at the Olympics, having missed the 1980 Summer Olympics in Moscow because of its partial support for the United States boycott.
