2021 Western & Southern Open – Men's singles
| Men's singles | |
|---|---|
| 2021 Western & Southern Open | |
| Champion | Alexander Zverev |
| Runner-up | Andrey Rublev |
| Score | 6–2, 6–3 |
| Draw | 56 (7 Q / 4 WC ) |
| Seeds | 16 |
Alexander Zverev defeated Andrey Rublev in the final, 6–2, 6–3 to win the men's singles tennis title at the 2021 Cincinnati Masters. It was his fifth Masters 1000 title and 17th career singles title on the ATP Tour.
Novak Djokovic was the reigning champion, but did not participate.