2021 US Open – Boys' singles
| Boys' singles | |
|---|---|
| 2021 US Open | |
| Champion | Daniel Rincón |
| Runner-up | Shang Juncheng |
| Score | 6–2, 7–6(8–6) |
Jonáš Forejtek was the defending champion, having won the previous edition in 2019, but was no longer eligible to participate in junior events.
Daniel Rincón won the title, defeating Shang Juncheng in the final, 6–2, 7–6(8–6).