List of champions of the 1898 U.S. National Championships tennis tournament (now known as the US Open). The men's tournament was held from August 15 to August 22 on the outdoor grass courts at the Newport Casino in Newport, Rhode Island. The women's tournament was held from June 14 to June 18 on the outdoor grass courts at the Philadelphia Cricket Club in Philadelphia, Pennsylvania. It was the 18th U.S. National Championships and the second Grand Slam tournament of the year.
See main article: 1898 U.S. National Championships – Men's singles. 
Malcolm Whitman defeated Dwight F. Davis 3–6, 6–2, 6–2, 6–1
See main article: 1898 U.S. National Championships – Women's singles. Juliette Atkinson defeated Marion Jones 6–3, 5–7, 6–4, 2–6, 7–5
Leo Ware / George Sheldon defeated Holcombe Ward / Dwight Davis 1–6, 7–5, 6–4, 4–6, 7–5
Juliette Atkinson / Kathleen Atkinson defeated Marie Wimer / Carrie Neely 6–1, 2–6, 4–6, 6–1, 6–2
Carrie Neely / Edwin P. Fischer defeated Helen Chapman / J.A. Hill 6–2, 6–4, 8–6