Greece was the host country for the 2004 Summer Olympics in Athens, from 13 to 29 August 2004. As the progenitor nation and in keeping with tradition, Greek athletes have competed at every Summer Olympics in the modern era, alongside Australia, Great Britain, and Switzerland. The Hellenic Olympic Committee fielded a total of 426 athletes to the Games, 215 men and 211 women, and had achieved automatic qualification places in all sports, with the exception of men's and women's field hockey. It was also the nation's largest team ever in Summer Olympic history since the first modern Games were held in 1896.
Australia, the previous host of the 2000 Olympics at Sydney, competed at the 2004 Summer Olympics in Athens, Greece from 13 to 29 August 2004. Australian athletes have competed in every Summer Olympic Games of the modern era. The Australian Olympic Committee sent a total of 470 athletes to the Games to compete in 29 sports.
Italy competed at the 2004 Summer Olympics in Athens, Greece, from the 13th to the 29th of August 2004. The country has competed at every Summer Olympic games in the modern era, except for the 1904 Summer Olympics in St. Louis. The Italian National Olympic Committee sent the nation's largest ever delegation in history to the Games. A total of 364 athletes, 229 men and 135 women, competed in 27 sports.
Germany 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 Summer Olympics after its reunification in 1990. The German Olympic Sports Confederation sent the nation's second largest delegation to the Games since its reunification. A total of 441 athletes, 250 men and 191 women, competed in 27 sports, and were nominated by DOSB at four occasions.
Russia 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 as an independent nation. The Russian Olympic Committee sent a total of 446 athletes to the Games, 244 men and 202 women, to compete in all sports, except baseball, field hockey, football, and softball.
China competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's ninth appearance at the Summer Olympics since its debut in 1952. A total of 384 Chinese athletes, 136 men and 248 women, were selected by the Chinese Olympic Committee to compete in 28 sports. For the third time in its Olympic history, China was represented by more female than male athletes.
Spain competed at the 2004 Summer Olympics in Athens, Greece, from August 13 to 29, 2004. This nation has competed in every Summer Olympic Games since its official debut in 1920. Spain, however, boycotted two editions, the 1936 Summer Olympics in Nazi Germany, and the 1956 Summer Olympics in Melbourne when it joined the Dutch-led boycott, as a protest to the Soviet invasion of Hungary. The Spanish Olympic Committee sent the nation's third largest delegation in history to the Games. A total of 317 athletes, 177 men and 140 women, competed in 26 sports.
New Zealand competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's twenty-second appearance at the Olympics since its debut in 1908 as part of Australasia. The New Zealand Olympic Committee sent a total of 148 athletes, 81 men, and 67 women to the Games to compete in 18 sports, surpassing a single athlete short of the record from Sydney four years earlier. Basketball and field hockey were the only team-based sports in which New Zealand had its representation at these Olympic Games. There was only a single competitor in archery, boxing, and fencing.
Argentina competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's twenty-first appearance at the Olympic Games, except for three different editions. Argentina did not attend 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. The sailor Carlos Espínola was the nation's flag bearer at the opening ceremony. 152 competitors, 106 men and 46 women, took part in 86 events in 22 sports.
Serbia and Montenegro competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Previously known as the Federal Republic of Yugoslavia, this was the nation's third and last joint appearance at the Summer Olympics before Serbia and Montenegro became separated independent states in 2006. The Olympic Committee of Serbia and Montenegro sent a total of 85 athletes to the Games, 78 men and 7 women, to compete in 14 sports. Men's basketball, football, volleyball, and water polo were the only team-based sports in which Serbia and Montenegro had its representation at these Games. There was only a single competitor in road cycling, judo, tennis, and wrestling.
Germany competed at the 2008 Summer Olympics in Beijing, People's Republic of China. A total of 439 athletes were nominated to participate in the Games. The German Olympic Sports Confederation nominated athletes on 29 May, 23 June and 15 July 2008. Reaching the qualification standard set by the relevant sport's international governing body did not automatically mean that the athlete was nominated for Beijing, as the DOSB had stricter qualification standards. An athlete needed to have a somewhat realistic chance for a top 12 position. An exception to this are the team events, as the number of competing teams is already very limited through the IOC standards, and a chance for a respective place is already given by the qualification.
Croatia competed at the 2008 Summer Olympics in Beijing, People's Republic of China.
A total of 433 competitors competed for Australia at the 2008 Summer Olympics in Beijing. The team was Australia's second largest away team after the 2004 Summer Olympics in Athens, which included a team of 482 competitors. Australian athletes have competed in every Summer Olympic Games of the modern era.
Italy competed at the 2008 Summer Olympics, held in Beijing, China. The country sent a delegation of 344 athletes to compete.
China was the host nation of the 2008 Summer Olympics. China was represented by the Chinese Olympic Committee (COC), and the team of selected athletes were officially known as Team China.
Spain competed at the 2008 Summer Olympics in Beijing, People's Republic of China, with a total of 286 athletes and competed in 25 sports.
South Korea competed at the 2008 Summer Olympics in Beijing, China. This is a list of all of the South Korean athletes who qualified for the Olympics and their results. South Korea sent a delegation of 267 athletes to these games.
The Russian Federation competed at the 2008 Summer Olympics, held in Beijing, China, represented by the Russian Olympic Committee. Russia competed in all sports except baseball, field hockey, football, softball, and taekwondo. They ranked third in the medal table by the number of gold (24) and overall (60) medals. Russia also had 14 medals stripped for doping violations, the most of any nation at the 2008 Olympics.
The Czech Republic participated in the 2008 Summer Olympics in Beijing, China. The Czech delegation consisted of around 130 athletes.
The United States of America (USA) competed at the 2004 Summer Olympics in Athens, Greece. 533 competitors, 279 men and 254 women, took part in 254 events in 31 sports.
China 
