1891 U.S. National Championships
Date	August 22 - August 31 (M) June 23 - June 27 (W)
Edition	11th
Category	Grand Slam
Surface	Grass
Location	Newport, R.I., United States (M) Philadelphia, PA, United States (W)
Champions
Men's singles
Oliver Campbell[1]
Women's singles
Mabel Cahill[1]
Men's doubles
Oliver Campbell / Bob Huntington
Women's doubles
Mabel Cahill / Emma Leavitt Morgan
← 1890 · U.S. National Championships · 1892 →

List of champions of the 1891 U.S. National Championships (now known as the US Open). The men's tournament was held from August 22 to August 31 on the outdoor grass courts at the Newport Casino in Newport, Rhode Island. The women's tournament was held from June 23 to June 27 on the outdoor grass courts at the Philadelphia Cricket Club in Philadelphia, Pennsylvania. It was the 11th U.S. National Championships and the second Grand Slam tournament of the year.:^[1]

Oliver Campbell defeated Clarence Hobart 2–6, 7–5, 7–9, 6–1, 6–2

Mabel Cahill defeated Ellen Roosevelt 6–4, 6–1, 4–6, 6–3

Oliver Campbell / Bob Huntington defeated Valentine Hall / Clarence Hobart 6–3, 6–4, 8–6

Mabel Cahill / Emma Leavitt Morgan defeated Grace Roosevelt / Ellen Roosevelt 2–6, 8–6, 6–4

Mabel Cahill / Wright defeated Grace Roosevelt / Lee 6–4, 6–0, 7–5 †

† - The Mixed Doubles event was not an official event in 1891

• Official US Open website