This was the 20th appearance of the event, which is one of 12 athletics events to have been held at every Summer Olympics. Returning runners from the 1980 marathon included silver medalist
Gerard Nijboer of the Netherlands, sixth-place finisher
Rodolfo Gómez of Mexico, ninth-place finisher (and 1972 silver and 1976 bronze medalist)
Karel Lismont of Belgium, and tenth-place finisher
Robert de Castella of Australia. The two-time defending champion,
Waldemar Cierpinski of East Germany, was prevented from trying for a third gold by the Eastern Bloc boycott. The two favorites were de Castella (1981 Fukuoka winner, in world record time, and 1983 World Championships winner) and
Toshihiko Seko of Japan (1981 Boston winner and 1978–1980 and 1983 Fukuoka winner).
Alberto Salazar of the United States had a strong 1980 to 1982 (1980–1982 New York winner and 1982 Boston winner), but had less good results in 1983, and had finished second at the USA trials. Botswana, the Central African Republic, Cyprus, Djibouti, Israel, Jamaica, Jordan, Oman, Qatar, the Virgin Islands, and Zaire each made their first appearance in Olympic men's marathons; the Republic of China made its first appearance as Chinese Taipei. The United States made its 19th appearance, most of any nation, having missed only the boycotted 1980 Games. ==Competition format and course==