The 2004 Summer Olympic Games, officially known as the Games of the XXVIII Olympiad, was a premier international multi-sport event held in Athens, Greece, from 13 to 29 August 2004 with the motto Welcome Home. 10,625 athletes competed, some 600 more than expected, accompanied by 5,501 team officials from 201 countries. There were 301 medal events in 28 different sports. Athens 2004 marked the first time since the 1996 Summer Olympics that all countries with a National Olympic Committee were in attendance. It was also the first time since 1896 (other than the since-downgraded 1906 Intercalated Games) that the Olympics were held in Greece.

A new medal obverse was introduced at these Games, replacing the design by Giuseppe Cassioli that had been used since the 1928 Games. This rectified the long lasting mistake of using a depiction of the Roman Colosseum rather than a Greek venue. The new design features the Panathinaiko Stadium.

The Summer Olympic Games or the Games of the Olympiad are an international multi-sport event, occurring every four years, organized by the International Olympic Committee. Medals are awarded in each event, with gold medals for first place, silver for second and bronze for third, a tradition that started in 1904. The Winter Olympics were also created due to the success of the summer Olympics.

The olympics have increased from a 42-event competition with fewer than 250 male athletes to a 300-event sporting celebration with over 10,000 competitors from 205 nations. Organizers for the 2008 Summer Olympics in Beijing expected approximately 10,500 athletes to take part in the 302 events on the program for the games.

The United States has hosted four Summer Olympics Games, more than any other nation. The United Kingdom will have hosted three Summer Olympics Games when they return to the British capital in 2012, all of them have been (and will be) in London, making it the first city to hold the Summer Olympic Games three times. Australia, France, Germany and Greece have all hosted the Summer Olympic Games twice. Other countries that have hosted the summer Olympics are Belgium, China, Canada, Finland, Italy, Japan, Mexico, Netherlands, South Korea, Spain, the Soviet Union and Sweden. In the 2016 Summer Olympics, Rio de Janeiro will host the first Summer Games in South America. Four cities have hosted two Summer Olympic Games: Los Angeles, London, Paris and Athens. Stockholm, Sweden, has hosted events at two Summer Olympic Games, having hosted the games in 1912 and the equestrian events at the 1956 Summer Olympics—which they are usually listed as jointly hosting. Events at the summer Olympics have also been held in Hong Kong and the Netherlands (both represented by their own NOCs), with the equestrian events at the 2008 Summer Olympics being held in Hong Kong and two sailing races at the 1920 Summer Olympics being held in the Netherlands.