The women's 400 metre individual medley event at the 2025 World Aquatics Championships was held on 3 August 2025 at the World Aquatics Championships Arena at the Singapore Sports Hub in Kallang, Singapore.

Background Summer McIntosh of Canada enters as the Olympic and 2023 World Champion with a world record of 4:23.65 and the three fastest times ever. She leads the 2025 rankings by 10 seconds. Emma Weyant (4:33.95) and Katie Grimes (4:37.22) are the top contenders from the United States, with Weyant showing stronger form this season.

Freya Colbert of Great Britain, the 2024 World Champion, comes in with a season best of 4:34.01. Teammate Abbie Wood, who recently returned to the event, has also been 4:36.66. Australians Ella Ramsay and Jenna Forrester, who finished first and second at the Australian Trials, are separated by 0.07 and both reached the final in Paris. Ireland’s Ellen Walshe and Japan’s Mio Narita are returning Olympic finalists. Both have set new personal bests this year—4:35.32 and 4:35.39, respectively—and are ranked top five globally.

China’s 12-year-old Yu Zidi swam 4:35.53 at the Chinese Nationals. While she lacks international experience, her time places her among the top contenders.

Qualification Each National Federation was permitted to enter a maximum of two qualified athletes in each individual event, but they could do so only if both of them had attained the "A" standard qualification time. For this event, the "A" standard qualification time was 4:43.06 seconds. Federations could enter one athlete into the event if they met the "B" standard qualification time. For this event, the "B" standard qualification time was 4:52.97 seconds. Athletes could also enter the event if they had met an "A" or "B" standard in a different event and their Federation had not entered anyone else. Additional considerations applied to Federations who had few swimmers enter through the standard qualification times. Federations in this category could at least enter two men and two women to the competition, all of whom could enter into up to two events. +Top 10 fastest qualification timesSwimmerCountryTimeCompetitionSummer McIntosh4:23.652025 Canadian Swimming TrialsKaylee McKeown4:28.222024 Australian ChampionshipsKatie Grimes4:33.402024 Summer OlympicsEmma Weyant4:33.95Fort Lauderdale stop of the 2025 TYR Pro Swim SeriesFreya Colbert4:34.012024 Great British ChampionshipsAnastasia Gorbenko4:34.87Monaco stop of the 2024 Mare Nostrum Swim TourVivien Jackl4:34.962024 Hungarian ChampionshipsEllen Walshe4:35.32Fort Lauderdale stop of the 2025 TYR Pro Swim SeriesMio Narita4:35.392025 Japanese ChampionshipsZidi Yu4:35.532025 Chinese Championships

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

Heats The heats took place at 10:28. RankHeatLaneSwimmerNationTimeNotes 1 3 4 Summer McIntosh 4:35.56 Q 2 3 7 Jenna Forrester 4:36.17 Q 3 2 6 Yu Zidi 4:36.49 Q 4 2 7 Waka Kobori 4:36.62 Q 5 3 5 Emma Weyant 4:36.75 Q 6 3 6 Mio Narita 4:37.12 Q 7 2 4 Katie Grimes 4:38.26 Q 8 2 5 Freya Colbert 4:38.31 Q 9 2 3 Ellen Walshe 4:38.72 10 3 1 Abbie Wood 4:41.73 11 3 3 Vivien Jackl 4:43.02 12 2 1 Chang Mohan 4:43.12 13 3 9 Emma Carrasco 4:44.47 14 3 0 Alba Vázquez 4:46.01 15 2 0 Aleksandra Knop 4:48.12 16 2 8 Viktória Mihályvári-Farkas 4:49.50 17 3 8 Sara Franceschi 4:50.23 18 1 4 Gwinn Applejean 4:51.16 19 1 5 Kim Bo-min 4:51.55 20 2 9 Kamonchanok Kwanmuang 4:53.21 21 1 3 Artemis Vasilaki 4:53.27 22 1 2 Ng Lai Wa 4:57.66 23 1 6 Kristen Romano 5:04.08 24 1 7 Inana Soleman 5:07.52 2 2 Ella Ramsay 3 2 Mary-Sophie Harvey

Final The final took place on 3 August at 20:14.

Rank Lane Name Nationality Time Notes 4 Summer McIntosh 4:25.78 CR 5 Jenna Forrester 4:33.26 7 Mio Narita 4:33.26 4 3 Yu Zidi 4:33.76 5 2 Emma Weyant 4:34.01 6 1 Katie Grimes 4:36.52 7 6 Waka Kobori 4:38.05 8 8 Freya Colbert 4:40.21

References