Swimming at the 2020 Summer Olympics – Men's 4 × 100 metre medley relay

The men's 4 × 100 metre medley relay event at the 2020 Summer Olympics was held on 30 July and 1 August 2021 at the Tokyo Aquatics Centre. It was the event's sixteenth consecutive appearance, having been held at every edition since 1960.

The United States extended their dominance in the event, having won it every time since its introduction in 1960, except for the boycotted 1980 Games.

Summary
In the final swimming race at these Games, the U.S. continued their unbeaten streak in the event to take gold in a world record time of 3:26.78, eclipsing the former super-suited mark by half a second. Though a shade off his bronze medal-winning time in the individual 100 m backstroke, Ryan Murphy (52.31) nonetheless got the U.S. out to an early lead of 0.21 seconds. While Michael Andrew's breaststroke split of 58.49 led the U.S. to fall back in third, Caeleb Dressel unleashed the fastest butterfly split of all time in 49.03 to regain the lead. Diving in with a margin of 6-tenths of a second over the field, Zach Apple anchored the U.S. home to gold in 46.95 for their eleventh swimming gold of the Games.

100 m breaststroke world record holder Adam Peaty threw down the fastest breaststroke split ever in 56.53 to give the British team of Luke Greenbank (53.63), James Guy (50.27), and Duncan Scott (47.08) a brief lead of 0.6 seconds on the second leg. Though the U.S. edged them out to the front in the following leg, Great Britain touched in a European record of 3:27.51 - the third fastest performance in history - to defend their silver medal from five years earlier in Rio.

Meanwhile, Italy's well-rounded foursome of Thomas Ceccon (52.52), Nicolò Martinenghi (58.11), Federico Burdisso (51.07) and Alessandro Miressi (47.47) posted a national record of 3:29.17 to secure Italy's first podium finish in the event. Despite a strong back-half - with Andrey Minakov (50.31) and Kliment Kolesnikov (47.03) recording the third-fastest butterfly and freestyle splits in the field - ROC could not close the gap on the Italians to miss the podium by 5-hundredths of a second. Australia, the defending bronze medallists, could not repeat their podium finish, falling to fifth in 3:29.60. Japan took sixth in 3:29.91, breaking China's 2018 Asian record by 0.08 s, while Canada (3:32.42) finished in a distant seventh. China was disqualified from the race owing to an early relay takeover by freestyler He Junyi.

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

The following record was established during the competition:

Qualification
The top 12 teams in this event at the 2019 World Aquatics Championships qualified for the Olympics. An additional 4 teams will qualify through having the fastest times at approved qualifying events during the qualifying period (1 March 2019 to 30 May 2020).

Competition format
The competition consists of two rounds: heats and a final. The relay teams 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)

Heats
The relay teams with the top 8 times, regardless of heat, advanced to the final.