Women's 400m Round 1 - Heat 3
mardi 3 août 2021, 01h01 GMT – 06h01 GMT
| Nom | Temps | |
|---|---|---|
| 1 |  Allyson Felix | 50.84″ |
| 2 |  Roneisha McGregor | + 0.3″ |
| 3 |  Lada Vondrova | + 0.3″ |
| 4 |  Ama Pipi | + 0.33″ |
| 5 |  Tiffani Silva Marinho | + 1.27″ |
| 6 |  Leni Shida | + 1.64″ |
| 7 | Samantha Dirks | + 3.32″ |
| 8 |  Tetyana Melnyk | + 4.15″ |