| Champ: |  Daniel Rincón |
| Runner: |  Shang Juncheng |
| Score: | 6–2, 7–6(8–6) |
| Before Year: | 2019 |
See main article: 2021 US Open (tennis).
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).[1]
All seeds received a bye into the second round.