1890 U.S. National Championships – Men's singles
| Men's singles | |
|---|---|
| 1890 U.S. National Championships | |
| Champion | Oliver Campbell |
| Runner-up | Henry Slocum |
| Score | 6–2, 4–6, 6–3, 6–1 |
Oliver Campbell defeated the two-time defending champion Henry Slocum in the challenge round, 6–2, 4–6, 6–3, 6–1 to win the men's singles tennis title at the 1890 U.S. National Championships. It was the first of three U.S. Championships titles for Campbell.