The men's 100 metres was a track and field athletics event held as part of the Athletics at the 1912 Summer Olympics programme. It was the fifth appearance of the event, which is one of 12 athletics events to have been held at every Summer Olympics. The competition was held on 6 July 1912 and on 7 July 1912. Seventy runners from 22 nations competed. NOCs could enter up to 12 athletes. The event was won by Ralph Craig of the United States, as the Americans swept the medals for a second time (previously having done so in 1904).