| Champ: |  Ilie Năstase |
| Runner: | Tom Okker |
| Score: | 3–6, 8–6, 6–1, 6–1 |
| Draw: | 32 |
| Seeds: | 8 |
| Main Name: | Monte-Carlo Masters |
The 1971 Monte Carlo Open – Men's singles was an event of the 1971 Monte Carlo Open tennis tournament. Željko Franulović was the defending champion but did not compete in this edition. Third-seeded Ilie Năstase won the singles title by defeating first-seeded Tom Okker 3–6, 8–6, 6–1, 6–1 in the final.[1] [2]