2018 IAAF World U20 Championships – Women's 400 metres
The women's 400 metres at the 2018 IAAF World U20 Championships was held at Ratina Stadium on 10, 11 and 12 July.
Records
Results
Heats
Qualification: First 4 of each heat and the 4 fastest times qualified for the semifinals.| Rank | Heat | Name | Nationality | Time | Note |
| 1 | 4 | Hima Das | IND | 52.25 | Q |
| 2 | 1 | Taylor Manson | USA | 52.68 | Q |
| 3 | 4 | Stacey-Ann Williams | JAM | 52.71 | Q, |
| 4 | 2 | Mary Moraa | KEN | 52.85 | Q, |
| 5 | 3 | Ella Connolly | AUS | 52.99 | Q, |
| 6 | 2 | Andrea Miklós | ROU | 53.14 | Q |
| 7 | 3 | Tiffani Silva | BRA | 53.18 | Q |
| 8 | 3 | Roxana Gómez | CUB | 53.19 | Q |
| 9 | 1 | Davicia Patterson | IRL | 53.20 | Q |
| 10 | 2 | Elisabetta Vandi | ITA | 53.51 | Q, |
| 11 | 1 | Stella Wonruku | UGA | 53.55 | Q |
| 12 | 2 | Frehiywot Wondie | ETH | 53.59 | Q |
| 13 | 1 | Sharelle Samuel | CAN | 53.62 | Q, |
| 14 | 4 | Ashlan Best | CAN | 53.91 | Q |
| 15 | 4 | Fiordaliza Cofil | DOM | 54.13 | Q |
| 16 | 5 | Jisna Mathew | IND | 54.32 | Q |
| 17 | 1 | Nuo Liang | CHN | 54.33 | q |
| 18 | 2 | Giovana Rosalia dos Santos | BRA | 54.35 | q |
| 19 | 5 | Amanda Crawford | GRN | 54.37 | Q |
| 20 | 1 | Angie Melisa Palacios | COL | 54.42 | q, |
| 21 | 3 | Shalysa Wray | CAY | 54.48 | Q |
| 22 | 4 | Yu Zhou | CHN | 54.49 | q, |
| 23 | 4 | Martina Weil | CHI | 54.52 | |
| 24 | 3 | Camilla Pitzalis | ITA | 54.59 | |
| 25 | 2 | Ciara Deely | IRL | 54.69 | |
| 26 | 5 | Veronica Vancardo | SUI | 54.93 | Q |
| 27 | 5 | Laura Kaufmann | GER | 54.96 | Q |
| 28 | 2 | Mette Baas | FIN | 55.42 | |
| 29 | 3 | Milagros Durán | DOM | 55.56 | |
| 30 | 5 | Symone Mason | USA | 55.66 | |
| 31 | 5 | Mahilet Fikre | ETH | 55.88 | |
| 32 | 4 | Tetyana Kaysen | UKR | 57.14 | |
| 33 | 3 | Nicola Gibbon | RSA | 57.90 | |
| 34 | 5 | Maria Alejandra Carmona | NCA | 58.39 | |
| 35 | 1 | Marlie Viljoen | RSA | 59.01 | |
| 36 | 1 | Aishath Himna Hassan | MDV | 59.76 | |
| 37 | 5 | Patricija Karlina Roshofa | LAT | 1:00.08 | |
| 3 | Rae-Anne Serville | TTO | |||
| 2 | Pamela Milano | VEN |
Semifinals
Qualification: First 2 of each heat and the 2 fastest times qualified for the final.| Rank | Heat | Name | Nationality | Time | Note |
| 1 | 1 | Hima Das | IND | 52.10 | Q |
| 2 | 1 | Andrea Miklós | ROU | 52.48 | Q |
| 3 | 3 | Ella Connolly | AUS | 52.78 | Q, |
| 4 | 3 | Mary Moraa | KEN | 52.98 | Q |
| 5 | 1 | Stacey-Ann Williams | JAM | 53.00 | q |
| 6 | 2 | Taylor Manson | USA | 53.00 | Q |
| 7 | 2 | Ashlan Best | CAN | 53.24 | Q, |
| 8 | 1 | Elisabetta Vandi | ITA | 53.24 | q, |
| 9 | 2 | Roxana Gómez | CUB | 53.26 | |
| 10 | 2 | Tiffani Silva | BRA | 53.30 | |
| 11 | 3 | Davicia Patterson | IRL | 53.57 | |
| 12 | 1 | Sharelle Samuel | CAN | 53.68 | |
| 13 | 2 | Jisna Mathew | IND | 53.86 | |
| 14 | 2 | Fiordaliza Cofil | DOM | 53.94 | |
| 15 | 1 | Yu Zhou | CHN | 54.00 | |
| 16 | 3 | Frehiywot Wondie | ETH | 54.14 | |
| 17 | 3 | Giovana Rosalia dos Santos | BRA | 54.30 | |
| 18 | 1 | Shalysa Wray | CAY | 54.32 | |
| 19 | 1 | Stella Wonruku | UGA | 54.32 | |
| 20 | 3 | Amanda Crawford | GRN | 54.36 | |
| 21 | 2 | Laura Kaufmann | GER | 54.91 | |
| 22 | 3 | Veronica Vancardo | SUI | 55.13 | |
| 23 | 3 | Nuo Liang | CHN | 55.51 | |
| 2 | Angie Melisa Palacios | COL |
Final
| Rank | Lane | Name | Nationality | Time | Note |
| 4 | Hima Das | IND | 51.46 | ||
| 3 | Andrea Miklós | ROU | 52.07 | ||
| 6 | Taylor Manson | USA | 52.28 | ||
| 4 | 5 | Ella Connolly | AUS | 52.82 | |
| 5 | 7 | Mary Moraa | KEN | 52.94 | |
| 6 | 1 | Stacey-Ann Williams | JAM | 53.23 | |
| 7 | 2 | Elisabetta Vandi | ITA | 53.40 | |
| 8 | 8 | Ashlan Best | CAN | 53.59 |