U devetom kolu su opet sve partije završene remijem, tako da je stanje na vrhu nepromjenjeno. Pobjedio je Vachier Lagrave sa 6 poena, a pola poena manje imaju Dominguez Perez, Fabiano Caruana i Wesley So. Na poslednjem mjestu je domaći igrač Dariusz Swiercz sa 2,5 poena.
Mamedyarov,S (2782) – Vachier Lagrave,M (2751) [D85]
8th Sinquefield Cup 2021 Saint Louis USA (9), 26.08.2021
1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.cxd5 Nxd5 5.e4 Nxc3 6.bxc3 Bg7 7.Nf3 c5 8.Rb1 0–0 9.Be2 cxd4 10.cxd4 Qa5+ 11.Bd2 Qxa2 12.0–0 Bg4 13.Rxb7 Bxf3 14.Bxf3 Bxd4 15.e5 Na6 16.Rxe7 Rad8 17.e6 fxe6 18.Qe1 Nc5 19.Bc3 Nd3
20.Bxd4 Nxe1 21.Rg7+ Kh8 22.Rd7+ Kg8 23.Rg7+ Kh8 24.Rd7+ Kg8 25.Rg7+ ½–½
| Round 9 (August 26, 2021) | ||||||
| So, Wesley | – Dominguez Perez, Leinier | ½-½ | 35 | D27 | QGA | |
| Rapport, Richard | – Caruana, Fabiano | ½-½ | 62 | B44 | Sicilian Paulsen | |
| Mamedyarov, Shakhriyar | – Vachier-Lagrave, Maxime | ½-½ | 25 | D85 | Gruenfeld Defence | |
| Shankland, Sam | – Swiercz, Dariusz | ½-½ | 43 | A07 | Barcza System | |
| Svidler, Peter | – Xiong, Jeffery | ½-½ | 44 | C55 | Two Knights Defence |
Konačno stanje
| 1. | Vachier-Lagrave, Maxime | g | FRA | 2751 | 6 |
| 2. | Dominguez Perez, Leinier | g | USA | 2758 | 5½ |
| 3. | Caruana, Fabiano | g | USA | 2806 | 5½ |
| 4. | So, Wesley | g | USA | 2772 | 5½ |
| 5. | Rapport, Richard | g | HUN | 2763 | 4½ |
| 6. | Xiong, Jeffery | g | USA | 2710 | 4 |
| 7. | Mamedyarov, Shakhriyar | g | AZE | 2782 | 4 |
| 8. | Shankland, Sam | g | USA | 2709 | 4 |
| 9. | Svidler, Peter | g | RUS | 2714 | 3½ |
| 10. | Swiercz, Dariusz | g | USA | 2655 | 2½ |