Final | | time | | L | 1. Marileidy Paulino | Dominicana | 48.17s | Or, Nr | 6 | 2. Salwa Eid Naser | Bahrain | 48.53s | SB | 8 | 3. Natalia Kaczmarek | Poland | 48.98s | | 7 | 4. Rhasidat Adeleke | Ireland | 49.28s | | 4 | 5. Amber Anning | Great Britain | 49.29s | Nr | 5 | 6. Alexis Holmes | United States | 49.77s | PB | 9 | 7. Sada Williams | Barbados | 49.83s | | 2 | 8. Henriette Jæger | Norway | 49.96s | | 3 |
World Record: Marita Koch, East Germany 47.60s Canberra, Australia 6 October 1985 | Olympic Record: Marie-José Pérec, France 48.25s Atlanta, United States 29 July 1996 | World Leading: Nickisha Pryce, Jamaica 48.57s London, United Kingdom 20 July 2024 |
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| First 2 and Best 2 times advanced to Final. |
Semi 1 | | time | | L | 1. Salwa Eid Naser | Bahrain | 49.08s | Q, SB | 7 | 2. Rhasidat Adeleke | Ireland | 49.95s | Q | 8 | 3. Henriette Jæger | Norway | 50.17s | q | 4 | 4. Lieke Klaver | Netherlands | 50.44s | | 6 | 5. Victoria Ohuruogu | Great Britain | 51.14s | | 3 | 6. Aaliyah Butler | United States | 51.18s | | 5 | 7. Gabby Scott | Puerto Rico | 51.22s | | 2 | 8. Junelle Bromfield | Jamaica | 51.93s | | 9 |
Semi 2 | | time | | L | 1. Marileidy Paulino | Dominicana | 49.21s | Q | 6 | 2. Alexis Holmes | United States | 50.00s | Q | 5 | 3. Laviai Nielsen | Great Britain | 50.69s | | 7 | 4. Nickisha Pryce | Jamaica | 50.77s | | 8 | 5. Andrea Miklós | Romania | 50.78s | | 9 | 6. Ella Onojuvwevwo | Nigeria | 51.05s | | 3 | 7. Susanne Gogl-Walli | Austria | 51.17s | | 4 | 8. Lurdes Gloria Manuel | Czechia | 51.42s | | 2 |
Semi 3 | | time | | L | 1. Natalia Kaczmarek | Poland | 49.45s | Q | 7 | 2. Amber Anning | Great Britain | 49.47s | Q, PB | 6 | 3. Sada Williams | Barbados | 49.89s | q | 4 | 4. Kendall Ellis | United States | 50.40s | | 2 | 5. Roxana Gómez | Cuba | 50.48s | | 5 | 6. Paola Morán | Mexico | 50.73s | | 9 | 7. Stacey-Ann Williams | Jamaica | 50.79s | | 8 | 8. Miranda Coetzee | South Africa | 51.60s | | 3 |
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