List of champions of the 1899 U.S. National Championships tennis tournament (now known as the US Open). The men's tournament was held from August 14 to August 21 on the outdoor grass courts at the Newport Casino in Newport, Rhode Island. The women's tournament was held from June 21 to June 24 on the outdoor grass courts at the Philadelphia Cricket Club in Philadelphia, Pennsylvania. It was the 19th U.S. National Championships and the second Grand Slam tournament of the year.
See main article: 1899 U.S. National Championships – Men's singles. 
Malcolm Whitman defeated J. Parmly Paret 6–1, 6–2, 3–6, 7–5
See main article: 1899 U.S. National Championships – Women's singles. Marion Jones defeated Maud Banks 6–1, 6–1, 7–5
Holcombe Ward / Dwight Davis defeated Leo Ware / George Sheldon 6–4, 6–4, 6–3
Jane Craven / Myrtle McAteer defeated Maud Banks / Elizabeth Rastall 6–1, 6–1, 7–5
Elizabeth Rastall / Albert Hoskins defeated Jane Craven / James Gardner 6–4, 6–0, ret.