Swimming at the 2004 Summer Olympics – Men's 100 metre freestyle

The men's 100 metre freestyle event at the 2004 Summer Olympics was contested at the Olympic Aquatic Centre of the Athens Olympic Sports Complex in Athens, Greece on August 17 and 18.

Dutch swimmer Pieter van den Hoogenband defended his Olympic title in the event, outside the record time of 48.17. Roland Mark Schoeman, who solidified South Africa's triumph to break a world record in the 400 m freestyle relay, took home the silver in 48.23. Australia's Ian Thorpe edged out Schoeman's teammate Ryk Neethling to clinch a bronze medal by 0.07 of a second, in his personal best of 48.56.

Two-time Olympic champion Alexander Popov finished only in ninth place by just two hundredths of a second (0.02) outside of the top 8 field from the semifinals (49.23). By the following year, Popov announced his retirement from swimming, and became a full-time member of the International Olympic Committee. Other notable swimmers who missed the final cut featured France's Frédérick Bousquet, Lithuania's Rolandas Gimbutis, Trinidad and Tobago's George Bovell, and U.S. duo Jason Lezak and Ian Crocker. This became the first 100m freestyle where not a single American even qualified for the semifinals.