2018 FINA World Swimming Championships (25 m) – Women's 400 metre individual medley
# 2018 FINA World Swimming Championships (25 m) – Women's 400 metre individual medley

The women's 400 metre individual medley competition of the 2018 FINA World Swimming Championships (25 m) was held on 11 December 2018.

## Records

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

| | Name | Nation | Time | Location | Date |
| - | - | - | - | - | - |
| World record | Mireia Belmonte | Spain | 4:18.94 | Netanya | 12 August 2017 |
| Championship record | Mireia Belmonte | Spain | 4:19.86 | Doha | 3 December 2014 |

## Results

### Heats

The heats were started at 11:05.

| Rank | Heat | Lane | Name | Nationality | Time | Notes |
| - | - | - | - | - | - | - |
| 1 | 3 | 4 | Katinka Hosszú | Hungary | 4:23.59 | Q |
| 2 | 2 | 3 | Fantine Lesaffre | France | 4:27.74 | Q |
| 3 | 2 | 6 | Lara Grangeon | France | 4:27.91 | Q |
| 4 | 2 | 5 | Ilaria Cusinato | Italy | 4:28.02 | Q |
| 5 | 3 | 1 | Melanie Margalis | United States | 4:29.14 | Q |
| 6 | 2 | 4 | Catalina Corro | Spain | 4:31.02 | Q |
| 7 | 3 | 6 | Sakiko Shimizu | Japan | 4:31.12 | Q |
| 8 | 3 | 5 | Miho Takahashi | Japan | 4:31.13 | Q |
| 9 | 3 | 2 | Abbey Harkin | Australia | 4:33.23 | |
| 10 | 2 | 2 | Leah Smith | United States | 4:34.93 | |
| 11 | 3 | 3 | Zhou Min | China | 4:35.34 | |
| 12 | 1 | 3 | Florencia Perotti | Argentina | 4:36.68 | |
| 13 | 2 | 0 | Nguyễn Thị Ánh Viên | Vietnam | 4:37.28 | |
| 14 | 3 | 7 | Barbora Závadová | Czech Republic | 4:37.33 | |
| 15 | 3 | 8 | Jimena Pérez | Spain | 4:37.42 | |
| 16 | 2 | 7 | Irina Krivonogova | Russia | 4:37.54 | |
| 17 | 2 | 1 | Victoria Kaminskaya | Portugal | 4:38.49 | |
| 18 | 3 | 0 | Rebecca Meder | South Africa | 4:39.31 | |
| 19 | 1 | 6 | Claudia Hufnagl | Austria | 4:39.76 | |
| 20 | 2 | 9 | Diana Durães | Portugal | 4:39.81 | |
| 21 | 3 | 9 | Katja Fain | Slovenia | 4:40.00 | |
| 22 | 1 | 5 | Viktoriya Zeynep Güneş | Turkey | 4:40.67 | |
| 23 | 2 | 8 | Anastasiia Sorokina | Russia | 4:41.43 | |
| 24 | 1 | 2 | Ruby Matthews | New Zealand | 4:43.91 | |
| 25 | 1 | 7 | Lam Hoi Kiu | Hong Kong | 4:47.47 | |
| 26 | 1 | 4 | Tereza Horáková | Czech Republic | 4:48.83 | |
| 27 | 1 | 8 | Hamida Rania Nefsi | Algeria | 4:53.29 | |
| 28 | 1 | 1 | Wang Wan-chen | Chinese Taipei | 4:54.25 | |
| 29 | 1 | 0 | Sára Niepelová | Slovakia | 4:54.87 | |
| 30 | 1 | 9 | Daniela Alfaro | Costa Rica | 5:01.36 | NR |

### Final

The final was held at 19:48.

| Rank | Lane | Name | Nationality | Time | Notes |
| - | - | - | - | - | - |
| | 4 | Katinka Hosszú | Hungary | 4:21.40 | |
| | 2 | Melanie Margalis | United States | 4:25.84 | |
| | 5 | Fantine Lesaffre | France | 4:27.31 | =NR |
| 4 | 6 | Ilaria Cusinato | Italy | 4:27.88 | |
| 5 | 3 | Lara Grangeon | France | 4:29.56 | |
| 6 | 1 | Sakiko Shimizu | Japan | 4:31.07 | |
| 7 | 7 | Catalina Corro | Spain | 4:31.63 | |
| 8 | 8 | Miho Takahashi | Japan | 4:35.62 | |
