Swimming at the 1948 Summer Olympics – Men's 100 metre freestyle

This was the 10th 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]

None of the seven finalists from the pre-World War II 1936 Games returned. Alex Jany, a teenager from France, was the favorite in the event. The American team, including world record holder Alan Ford, was also strong.[2] Ford had beaten Jany's record a month before the Games.

Cuba, Iceland, India, and Mexico each made their debut in the event. The United States made its 10th appearance, having competed at each edition of the event to date.

The competition used a three-round (quarterfinals, semifinals, final) format. The advancement rule was a modification of the one used since 1912, allowing the top swimmers in each race plus one or more wild cards to advance. For this event, the top two in each preliminary heat plus the next four fastest swimmers would advance to the semifinals; the top three in each semifinal plus the next two fastest swimmers would move on to the final. There were 6 heats of between 6 and 8 swimmers, allowing 16 swimmers to advance to the semifinals. The 2 semifinals had 8 swimmers each; 8 advanced to the final.

This swimming event used freestyle swimming, which means that the method of the stroke is not regulated (unlike backstroke, breaststroke, and butterfly events). Nearly all swimmers use the front crawl or a variant of that stroke. Because an Olympic-size swimming pool is 50 metres long, this race consisted of two lengths of the pool.

These were the standing world and Olympic records (in seconds) prior to the 1948 Summer Olympics.

World record	Alan Ford (USA)	55.4	New Haven, United States	29 June 1948
Olympic record	Masaharu Taguchi (JPN)	57.5	Berlin, Germany	8 August 1936

Wally Ris equaled the Olympic record in the second semifinal with 57.5 seconds, then beat it with 57.3 seconds in the final.