The World Aquatics Junior Swimming Championships is an international swimming championship event organized biennially by World Aquatics for swimmers aged 14–18 years as of the 31st December of the year of the competition. It is usually held on odd years. Prior to 2023, the event was known as the FINA World Junior Swimming Championships and was open to female swimmers aged 14–17 and male swimmers aged 15–18 as of the 31st of December of the year of the competition.
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 heats for the men's 50 metre freestyle race at the 2009 World Championships took place on 31 July and 1 August 2009 (final) at the Foro Italico in Rome, Italy.
The men's 200-metre butterfly event at the 2001 World Aquatics Championships took place between 23 July – 24 July. Both the heats and semifinals were held on 23 July with the heats being held in the morning session and the semifinals being held in the evening session. The final was held on 24 July.
The men's 50 metre freestyle event at the 2005 World Aquatics Championships was held on 29 and 30 July 2005 at the Parc Jean-Drapeau in Montreal, Canada.
The men's 50 metre freestyle event at the 2001 World Aquatics Championships was held on 22 and 23 July 2001 (final) at the Fukuoka, Japan.
The men's 200 metre individual medley competition of the swimming events at the 2011 World Aquatics Championships took place July 27 and 28. The heats and semifinals took place July 27 and the final was held July 28.
The men's 100 metre freestyle event at the 2001 World Aquatics Championships took place 27 July. The heats and semifinals were held on 26 July.
The men's 200-metre freestyle event at the 2001 World Aquatic Championships took place 25 July. The heats and semifinals were on 24 July.
The men's 50 metre backstroke event at the 2001 World Aquatics Championships took place 25 July. The heats and semifinals took place 24 July, with the final being held on 25 July.
The men's 50 metre butterfly event in swimming at the 2013 World Aquatics Championships took place on 28–29 July at the Palau Sant Jordi in Barcelona, Spain.
The women's 100 metre breaststroke event at the 2016 Summer Olympics took place on 7–8 August at the Olympic Aquatics Stadium.
The men's 50 metre freestyle event at the 2020 Summer Olympics was held from 30 July to 1 August 2021 at the Tokyo Aquatics Centre. It was the event's tenth appearance, first held in 1904 and then at every edition since 1988. The event is nicknamed the "splash and dash" event.
The women's 50 metre freestyle event at the 2020 Summer Olympics was held from 30 July to 1 August 2021 at the Olympic Aquatics Centre. It was the event's ninth consecutive appearance, having been held at every edition since 1988.
The men's 100 metre breaststroke event at the 2020 Summer Olympics was held from 24 to 26 July 2021 at the Tokyo Aquatics Centre. It was the event's fourteenth consecutive appearance, having been held at every edition since 1968.
The men's 200 metre breaststroke event at the 2020 Summer Olympics was held from 27 to 29 July 2021 at the Tokyo Aquatics Centre. It was the event's twenty-sixth consecutive appearance, having been held at every edition since 1908.
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 butterfly event at the 2020 Summer Olympics was held from 27 to 29 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 50 metre freestyle event at the 2001 World Aquatics Championships was held on 28 and 29 July 2001 (final) at the Fukuoka, Japan.
