Swimming at the 2018 Summer Youth Olympics – Girls' 800 metre freestyle
The girls' 800 metre freestyle event at the 2018 Summer Youth Olympics took place on 9 October at the Natatorium in Buenos Aires, Argentina.Results
The heats were started at 10:00 and 18:00.
| Rank | Heat | Lane | Name | Nationality | Time | Notes |
| 3 | 5 | Ajna Késely | | 8:27.60 | |
| 3 | 4 | Delfina Pignatiello | | 8:32.42 | |
| 3 | 2 | Marlene Kahler | | 8:36.57 | |
| 3 | 8 | Delfina Dini | | 8:43.71 | |
| 3 | 3 | Celine Rieder | | 8:43.73 | |
| 2 | 3 | Gan Ching Hwee | | 8:44.69 | |
| 3 | 1 | Kaitlynn Sims | | 8:46.40 | |
| 2 | 6 | María Román | | 8:48.88 | |
| 3 | 6 | Maddie Donohoe | | 8:48.96 | |
| 10 | 3 | 7 | Andrea Galisteo | | 8:49.85 | |
| 11 | 2 | 5 | Nicole Oliva | | 8:52.29 | |
| 12 | 2 | 1 | Malene Rypestøl | | 8:54.64 | |
| 13 | 2 | 2 | Samantha Bello | | 8:54.89 | |
| 14 | 1 | 4 | Erika Fairweather | | 8:56.14 | |
| 15 | 1 | 5 | Arianna Valloni | | 8:57.00 | |
| 16 | 2 | 4 | Kate Beavon | | 8:59.60 | |
| 17 | 2 | 7 | Tinky Ho | | 9:02.08 | |
| 18 | 2 | 8 | Alexandra Frazão | | 9:05.25 | |
| 19 | 1 | 3 | Sandy Atef | | 9:16.73 | |
| 20 | 1 | 6 | Vasiliki Kadoglu | | 9:18.92 | |
| 21 | 1 | 2 | Jennifer Ramírez | | 9:28.18 | |
