Swimming at the 1908 Summer Olympics – Men's 400 metre freestyle
| Men's 400 metre freestyle at the Games of the IV Olympiad  | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Venue | White City Stadium | ||||||||||||
| Dates | July 13–16 | ||||||||||||
| Competitors | 25 from 10 nations | ||||||||||||
| Medalists | |||||||||||||
  | |||||||||||||
| Swimming at the 1908 Summer Olympics  | |
|---|---|
| Freestyle | |
| 100 m | men | 
| 400 m | men | 
| 1500 m | men | 
| Backstroke | |
| 100 m | men | 
| Breaststroke | |
| 200 m | men | 
| Freestyle relay | |
| 4 × 200 m | men | 
The men's 400 metre freestyle was one of six swimming events on the swimming at the 1908 Summer Olympics programme. Its distance was the median of the 3 individual freestyle event distances. It was the first time an event over 400 metres was held at the Olympics (after a 440-yard contest was held in 1904). The competition was held from Monday July 13, 1908 to Thursday July 16, 1908.
Each nation could enter up to 12 swimmers. Twenty-five swimmers from ten nations competed. The winning margin was 7.4 seconds which as of 2023 is the only time this event has been won by more than six seconds at the Olympics.