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.
Turkey competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Turkish athletes have competed at every Summer Olympic Games since its debut in 1908. Turkey did not attend the 1920 Summer Olympics in Antwerp, the 1932 Summer Olympics in Los Angeles at the period of worldwide Great Depression, and the 1980 Summer Olympics in Moscow because of its support for the United States boycott. The Turkish Olympic Committee sent the nation's largest delegation to the Games. A total of 65 athletes, 45 men and 20 women, competed in 10 sports. There was only a single competitor in shooting and taekwondo.
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.
Luxembourg competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. The nation has competed at every Olympic games for a century, except the 1932 Summer Olympics in Los Angeles.
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.
Namibia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's fourth consecutive appearance at the Olympics.
Ghana competed at the 2004 Summer Olympics in Athens, Greece from 13 to 29 August 2004.
São Tomé and Príncipe competed at the 2004 Summer Olympics in Athens, Greece, which was held from 13 to 29 August 2004. The country's participation at Athens marked its third appearance in the Summer Olympics since its debut in the 1996 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.
Cambodia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 April 2004.
Brunei, as Brunei Darussalam, competed at the 2004 Summer Olympics in Athens, Greece, which took place between 13 and 29 August 2004. The country's participation in Athens marked its fourth appearance at the Summer Olympics since its debut in the 1988 Summer Olympics.
Grenada competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's sixth consecutive appearance at the Olympics.
Mauritania competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. The country's participation at Athens marked its sixth appearance in the Summer Olympics since its debut in the 1984 Summer Olympics. The delegation included two track and field athletes, Youba Hmeida and Aminata Kamissoko, who were both selected by wildcards after both failed to meet either the "A" or "B" qualifying standards. Hmeida was selected as the flag bearer for the opening ceremony. Neither of the Mauritanians progressed beyond the heats.
The Republic of the Congo competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004.
Morocco 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, except the 1980 Summer Olympics in Moscow, because of its partial support to the United States boycott.
Qatar competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004.
Palestine competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004.
North Korea competed as the Democratic People's Republic of Korea at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's seventh appearance at the Olympics since its debut in 1972. North Korean athletes did not attend the 1984 Summer Olympics in Los Angeles, when they joined the Soviet boycott, and subsequently, led a boycott at the 1988 Summer Olympics in Seoul, along with six other nations.
Saint Lucia competed at the 2004 Summer Olympics in Athens, Greece from 13 to 29 August 2004. Saint Lucia's athletes marched out first at the parade of nations at the Opening Ceremony as the first country in order of the Greek alphabet, and because hosts Greece marched last instead of their usual position at the head of the parade.
Ethiopia competed at the 2012 Summer Olympics in London, from 27 July to 12 August 2012. This was the nation's twelfth appearance at the Olympics, having missed three occasions because of the African, Soviet, and North Korean boycott. The Ethiopian Olympic Committee sent a total of 35 athletes to the Games, 18 men and 17 women, to compete only in athletics, specifically in the middle and long-distance running events, and swimming, the nation's Olympic debut.
