The women's 800 metre freestyle event at the 2025 World Aquatics Championships was held from 1 to 2 August 2025 at the World Aquatics Championships Arena at the Singapore Sports Hub in Kallang, Singapore.

Background The event was expected to feature a duel between Katie Ledecky of the United States and Summer McIntosh of Canada, who were both in career-best form. The Guardian wrote that the event was "set to be the defining moment" of the Championships, and that it "could signal a passing of the torch" from the older Ledecky to the younger McIntosh. CBC Sports commented that the race "looks like a classic sports story: the rising superstar vs. the wily veteran".

Ledecky had broken her own world record at the Fort Lauderdale stop of the 2025 TYR Pro Swim Series with 8:04.12 and had swum 8:05.76 at United States Nationals. She also held the championship record of 8:07.39, set at the 2015 World Championships. McIntosh, who had swum 8:05.07 at Canadian Trials to become the second-fastest performer in history, had improved her best by over four seconds in 2025.

Lani Pallister of Australia, who recorded 8:10.84 at Australian Trials to rank third all-time, was the leading contender for bronze. Also in contention were Li Bingjie of China, Simona Quadarella of Italy, Claire Weinstein of the United States, Isabel Gose of Germany, and Anastasiya Kirpichnikova of France, all with best times between 8:13 and 8:18.

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 8:34.62. 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 8:52.63. 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 timesSwimmerCountryTimeCompetitionKatie Ledecky8:04.122025 TYR Pro Swim Series (Fort Lauderdale)Summer McIntosh8:05.072025 Canadian TrialsLani Pallister8:10.842025 Australian TrialsSimona Quadarella8:14.552024 Summer OlympicsIsabel Gose8:17.822024 Summer OlympicsAnastasiya Kirpichnikova8:19.632024 Summer OlympicsClaire Weinstein8:19.672025 United States ChampionshipsLi Bingjie8:20.682025 Chinese ChampionshipsErika Fairweather8:21.672025 New Zealand ChampionshipsSofia Diakova  Neutral Athletes B8:24.932025 Russian Championships

Heats The heats took place on 1 August at 12:11. Ledecky swam the fastest qualifying time of 8:14.62, Pallister swam the second fastest time with 8:17.06, and McIntosh swam the third fastest time of 8:19.88.

RankHeatLaneSwimmerNationTimeNotes 1 3 4 Katie Ledecky 8:14.62 Q 2 3 5 Lani Pallister 8:17.06 Q 3 2 4 Summer McIntosh 8:19.88 Q 4 3 3 Isabel Gose 8:20.21 Q 5 2 5 Simona Quadarella 8:20.47 Q 6 3 2 Erika Fairweather 8:22.22 Q 7 2 6 Li Bingjie 8:23.23 Q 8 2 7 Ichika Kajimoto 8:27.51 Q 9 3 1 Yang Peiqi 8:27.89 10 3 8 Caitlin Deans 8:28.72 11 2 3 Anastasiya Kirpichnikova 8:28.97 12 3 7 Moesha Johnson 8:30.85 13 2 9 Gan Ching Hwee 8:31.36 NR 14 2 2 Sofia Diakova    Neutral Athletes B 8:33.16 15 2 8 Maya Werner 8:35.28 16 2 1 Ksenia Misharina    Neutral Athletes B 8:35.94 17 3 6 Claire Weinstein 8:38.70 18 1 3 Kristel Kobrich 8:39.78 19 1 4 Artemis Vasilaki 8:42.72 20 2 0 Vivien Jackl 8:43.29 21 3 9 Viktória Mihályvári-Farkas 8:46.46 22 3 0 Gabrielle Roncatto 8:48.32 23 1 6 Kim Chae-yun 8:48.92 24 1 5 Diana Durães 8:49.84 25 1 1 Catherine van Rensburg 8:50.60 26 1 7 Thilda Häll 8:52.60 27 1 0 Jamila Boulakbech 8:54.75 28 1 8 Anna Kalandadze 8:55.29 29 1 2 Delfina Dini 8:58.17 30 1 9 Harper Barrowman 9:21.03

Final The final took place on 2 August at 20:21.

Rank Lane Name Nationality Time Notes 4 Katie Ledecky 8:05.62 CR 5 Lani Pallister 8:05.98 OC 3 Summer McIntosh 8:07.29 4 2 Simona Quadarella 8:12.81 ER 5 1 Li Bingjie 8:15.59 6 6 Isabel Gose 8:18.23 7 7 Erika Fairweather 8:20.79 8 8 Ichika Kajimoto 8:26.85

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