1890 U.S. National Championships – Men's singles

Men's singles
1890 U.S. National Championships
Champion Oliver Campbell
Runner-up Henry Slocum
Score6–2, 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.