Swimming at the 2020 Summer Olympics – Men's 400 metre individual medley

The men's 400 metre individual medley event at the 2020 Summer Olympics was held on 24 and 25 July 2021 at the Tokyo Aquatics Centre. It was the event's fifteenth consecutive appearance, having been held at every edition since 1964.

Summary
In the first swimming final at these Games, the U.S.' Chase Kalisz used a scintillating breaststroke leg to upgrade his silver from Rio five years earlier with an Olympic title in the event. In the slowest Olympic final since 2000, Kalisz was the only finalist to improve on his heat time, clocking 4:09.42 to take the win. Kalisz's teammate Jay Litherland closed strongly in the final freestyle leg but could not overtake Kalisz, taking silver in 4:10.28 to deliver a U.S. quinella.

Australia's Brendon Smith (4:10.38) almost pulled off a last-to-first victory, sitting in eighth heading into the freestyle before splitting a blistering 56.3 to take bronze. With the podium finish, Smith claimed his nation's first medal in the event since Robert Woodhouse also won bronze in 1984. Only two-tenths of a second back, Hungary's Dávid Verrasztó and Great Britain's Max Litchfield were shut out of the medals, tying for fourth in 4:10.59. France's Léon Marchand (4:11.16), New Zealand's Lewis Clareburt (4:11.22) and Italy's Alberto Razzetti rounded out the tight field, with first to eighth separated by just two seconds.

Notable swimmers to miss the final included Japan's reigning World champion Daiya Seto who finished ninth in the heats, only 0.32 seconds behind the last qualifier. Fellow countryman Kosuke Hagino elected to not defend his Olympic title.

The medals for the competition were presented by Austria's IOC member Karl Stoss and the gifts were presented by Kuwait's FINA President Husain Al-Musallam.

Records
Prior to this competition, the existing world and Olympic records were as follows.

No new records were set during the competition.

Qualification
The Olympic Qualifying Time for the event is 4:15.84. Up to two swimmers per National Olympic Committee (NOC) can automatically qualify by swimming that time at an approved qualification event. The Olympic Selection Time is 4:21.46. Up to one swimmer per NOC meeting that time is eligible for selection, allocated by world ranking until the maximum quota for all swimming events is reached. NOCs without a male swimmer qualified in any event can also use their universality place.

Competition format
The competition consists of two rounds: heats and a final. The swimmers with the best 8 times in the heats advance to the final. Swim-offs are used as necessary to break ties for advancement to the next round.

Schedule
All times are Japan Standard Time (UTC+9)

Results
The swimmers with the top 8 times, regardless of heat, advanced to the final.