Swimming at the 1920 Summer Olympics – Men's 100 metre freestyle

This was the fifth appearance of the men's 100 metre freestyle. The event has been held at every Summer Olympics except 1900 (when the shortest freestyle was the 200 metres), though the 1904 version was measured in yards rather than metres.[2]

One of the six finalists from 1912 returned: gold medalist Duke Kahanamoku of the United States. The favorites were Kahanamoku and fellow American Norman Ross, the 1919 Inter-Allied Games winner. Kahanamoku had broken the world record in 1918.

Brazil, Czechoslovakia, Japan, Luxembourg, and Switzerland each made their debut in the event; Australia made its first appearance separate from New Zealand (the two had previously competed together as Australasia). The United States made its fifth appearance, having competed at each edition of the event to date. Hungary missed the event for the first time, with the nation not invited to the Games after World War I.

The competition used a three-round (quarterfinals, semifinals, final) format. The advancement rule was the same used in 1912; for each round before the final, the top two in each heat plus the fastest third-place swimmer would advance. There were 6 quarterfinals of between 4 and 7 swimmers, allowing 13 swimmers to advance to the semifinals. The 2 semifinals had 6 or 7 swimmers; 5 advanced to the final.

These were the standing world and Olympic records (in minutes) prior to the 1920 Summer Olympics.

World record	Duke Kahanamoku (USA)	1:01.4	New York City, United States	9 August 1918
Olympic record	Duke Kahanamoku (USA)	1:02.4	Stockholm, Sweden	7 July 1912

In the first heat Duke Kahanamoku set a new Olympic record with 1:01.8 minutes. In the semi-final he equalled the standing world record with 1:01.4 minutes. In the final which was later re-swum Kahanamoku set a new world record with 1:00.4 minutes, in the second final he equalled his record of 1:01.4 minutes again.

• Belgium Olympic Committee (1957). Olympic Games Antwerp 1920: Official Report (in French).
• Wudarski, Pawel (1999). "Wyniki Igrzysk Olimpijskich" (in Polish). Retrieved 25 April 2008.