| Men's Singles | |
|---|---|
| 1890 U.S. National Championships | |
| Champion | Oliver Campbell |
| Runner-up | Henry Slocum |
| Final score | 6–2, 4–6, 6–3, 6–1 |
Oliver Campbell won his first of three titles at the U.S. championships. He beat last year's champion Henry Slocum in four sets in the challenge round.