Athletics at the 1948 Summer Olympics – Men's 400 metres

This was the eleventh appearance of the event, which is one of 12 athletics events to have been held at every Summer Olympics. Bill Roberts of Great Britain was the only finalist from 1936 to return after the 12-year gap. Herb McKenley of Jamaica was the "heavy favorite," having recently broken the world record. Top challengers included fellow Jamaican Arthur Wint and American Mal Whitfield (fresh off a win in the 800 metres).[1]

In addition to Jamaica winning gold in its first appearance in the event, Bermuda, Ceylon, Colombia, Cuba, Iceland, Iraq, Turkey, and Yugoslavia competed in the 400 metres for the first time. The United States made its eleventh appearance in the event, the only nation to compete in it at every Olympic Games to that point.

The competition retained the basic four-round format from 1920. There were 12 heats in the first round, each with between 3 and 5 athletes. The top two runners in each heat advanced to the quarterfinals. There were 4 quarterfinals of 6 runners each; the top three athletes in each quarterfinal heat advanced to the semifinals. The semifinals featured 2 heats of 6 runners each. The top two runners in each semifinal heat advanced, making a six-man final.[1][3]

Prior to the competition, the existing World and Olympic records were as follows.

World record	Herb McKenley (JAM)	45.9	Milwaukee, United States	2 July 1948
Olympic record	Bill Carr (USA)	46.2	Los Angeles, United States	5 August 1932

All times are British Summer Time (UTC+1)

• Organising Committee for the XIV Olympiad, The (1948). The Official Report of the Organising Committee for the XIV Olympiad. LA84 Foundation. Retrieved 5 September 2016.