The women's 400 metres event at the 2019 European Athletics U23 Championships was held in Gävle, Sweden, at Gavlehov Stadium Park on 12 and 13 July.[1]
| width=200 bgcolor=gold | Gold | width=200 bgcolor=silver | Silver | width=200 bgcolor=CC9966 | Bronze |
| Natalia Kaczmarek | Lada Vondrová | Andrea Miklos |
Qualification: First 2 in each heat (Q) and next 2 fastest (q) qualified for the final.
| Rank | Heat | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 3 | 52.61 | Q | |||
| 2 | 1 | 52.72 | Q, PB | |||
| 3 | 3 | 52.99 | Q | |||
| 4 | 2 | 53.11 | Q | |||
| 5 | 1 | 53.26 | Q | |||
| 6 | 1 | 53.28 | q | |||
| 7 | 2 | 53.42 | Q | |||
| 8 | 2 | 53.51 | q | |||
| 9 | 3 | 53.67 | PB | |||
| 10 | 3 | 54.00 | ||||
| 11 | 3 | 54.64 | ||||
| 12 | 2 | 54.65 | ||||
| 13 | 1 | 54.80 | SB | |||
| 14 | 2 | 55.10 | ||||
| 15 | 2 | 55.44 | ||||
| 16 | 1 | 55.61 | ||||
| 17 | 3 | 55.67 | SB | |||
| 18 | 1 | 56.85 | ||||
| 19 | 3 | PB | ||||
| 1 | R163.3 (a)[2] |
| Rank | Lane | Name | Nationality | Time | Notes | ||
|---|---|---|---|---|---|---|---|
| 5 | align=left | 52.34 | PB | ||||
| 4 | align=left | 52.40 | |||||
| 7 | align=left | 52.66 | SB | ||||
| 4 | 3 | align=left | 52.94 | ||||
| 5 | 6 | align=left | 53.16 | ||||
| 6 | 8 | align=left | 53.20 | ||||
| 7 | 1 | align=left | 53.57 | ||||
| 8 | 2 | align=left | 53.64 |