This article includes the world record progression for the 4×100 metres medley relay, and it shows the chronological history of world record times in that competitive swimming event. The 4×100 metres medley relay is a medley race in which each of four swimmers on a team swims a 100-metre leg of the relay, each swimming a different stroke, in the following sequence:
- Backstroke
- Breaststroke
- Butterfly
- Freestyle.
The men's 400 metres at the 2008 Summer Olympics took place on 18–21 August at the Beijing National Stadium. Fifty-five athletes from 40 nations competed.
The women's 50 metre breaststroke competition of the 2014 FINA World Swimming Championships was held on 3 December with the heats and the semifinals and 4 December with the final.
The Men's 100 metre backstroke competition of the 2014 FINA World Swimming Championships was held on 3 December with the heats and the semifinals and 4 December with the final.
The men's 100 metre breaststroke competition of the 2014 FINA World Swimming Championships was held on 3 December with the heats and the semifinals and 4 December with the final.
The women's 100 metre backstroke competition of the 2014 FINA World Swimming Championships was held on 3 December with the heats and the semifinals and 4 December with the final.
The men's 100 metre butterfly competition of the 2014 FINA World Swimming Championships was held on 3 December with the heats and the semifinals and 4 December with the final.
The Women's 100 metre freestyle competition of the 2014 FINA World Swimming Championships was held on 4 December with the heats and the semifinals and 5 December with the final.
The Women's 50 metre butterfly competition of the 2014 FINA World Swimming Championships was held on 4 December with the heats and the semifinals and 5 December with the final.
The Men's 50 metre freestyle competition of the 2014 FINA World Swimming Championships was held on 4 December with the heats and the semifinals and 5 December with the final.
The Women's 100 metre individual medley competition of the 2014 FINA World Swimming Championships was held on 4 December with the heats and the semifinals and 5 December with the final.
The Men's 50 metre backstroke competition of the 2014 FINA World Swimming Championships was held on 5 December with the heats and the semifinals and 6 December with the final.
The Women's 50m Freestyle competition of the 2014 FINA World Swimming Championships was held on 6 December with the heats and the semifinals and 7 December with the final.
The Men's 100 metre individual medley competition of the 2014 FINA World Swimming Championships was held on 6 December with the heats and the semifinals and 7 December with the final.
The men's 200 metre freestyle competition of the swimming events at the 2015 World Aquatics Championships was held on 4 August with the heats and the semifinals on the 3 August.
Dirngulbai Moreyna "UB" Misech is a female Palauan swimmer and represents her country at international swimming competitions. She holds seven national records.
The Women's 100 metre freestyle competition of the 2016 FINA World Swimming Championships was held on 7 and 8 December 2016.
The women's 100 metre breaststroke event at the 2020 Summer Olympics was held from 25 July to 27 July 2021 at the Tokyo Aquatics Centre. It was the event's fourteenth consecutive appearance, having been held at every edition since 1968.
The women's 200 metre individual medley event at the 2020 Summer Olympics was held from 26 to 28 July 2021 at the Tokyo Aquatics Centre. It will be the event's twelfth appearance, having been first held in 1968 and 1972 and then at every edition since 1984.
The following table is an overview of national records in the 400 metres.
