List of champions of the 1890 U.S. National Championships (now known as the US Open). The men's singles and doubles competitions were held from August 18 to August 27 on the outdoor grass courts at the Newport Casino in Newport, Rhode Island. The women's singles and doubles competitions were held from June 10 to June 13 on the outdoor grass courts at the Philadelphia Cricket Club in Philadelphia, Pennsylvania. It was the 10th U.S. National Championships and the second Grand Slam tournament of the year.

Finals

Men's singles

🇺🇸 Oliver Campbell defeated 🇺🇸 Henry Slocum 6–2, 4–6, 6–3, 6–1

Women's singles

🇺🇸 Ellen Roosevelt defeated 🇺🇸 Bertha Townsend 6–2, 6–2

Men's doubles

🇺🇸 Valentine Hall / 🇺🇸 Clarence Hobart defeated 🇺🇸 Charles Carver / 🇺🇸 John Ryerson 6–3, 4–6, 6–2, 2–6, 6–3

Women's doubles

🇺🇸 Grace Roosevelt / 🇺🇸 Ellen Roosevelt defeated 🇺🇸 Bertha Townsend / 🇺🇸 Margarette Ballard 6–1, 6–2