The World Junior Records in Swimming are ratified by World Aquatics. They are the fastest times recorded by a swimmer aged 14 to 18 years, as of 31 December of the year of competition.
The long course (50 m pool) records were established in March 2014 and used the competition records from the World Junior Championships as standard times. Short course (25 m pool) records were established on 1 January 2015, and were shortly followed by the release of "Junior World Bests," which served as standard times for each event. Initially, the age groups were 15 to 18 years for boys and 14 to 17 years for girls. In 2023, they were changed to 14 to 18 years for all athletes.
Records are recognized for long course and short course in the following events: freestyle: 50, 100, 200, 400, 800 and 1500; backstroke: 50, 100 and 200; breaststroke: 50, 100 and 200; butterfly: 50, 100 and 200; Individual medley: 100 (short course only), 200 and 400; relays: 4×50 freestyle (short course only), 4×100 freestyle, 4×200 freestyle, 4×50 medley (short course only) and 4×100 medley; Mixed relays: 4×100 freestyle (long course only), 4×50 medley (short course only) and 4×100 medley (long course only).
All records were swum in finals unless noted otherwise.
Long Course (50 m) Boys
Girls
Mixed
Short Course (25 m) Boys
Girls
Mixed
Notes
References General World Junior Records – Men Long Course 30 September 2026 updated World Junior Records – Women Long Course 23 August 2024 updated World Junior Records – Mixed Relay Long Course 6 September 2023 updated World Junior Records – Men Short Course 17 April 2026 updated World Junior Records – Women Short Course 20 December 2025 updated World Junior Records – Mixed Relay Short Course 9 October 2021 updated Specific