List of champions of the 1904 U.S. National Championships tennis tournament (now known as the US Open). The men's tournament was held from August 21 to August 31 on the outdoor grass courts at the Newport Casino in Newport, Rhode Island. The women's tournament was held from June 21 to June 25 on the outdoor grass courts at the Philadelphia Cricket Club in Philadelphia, Pennsylvania. It was the 24th U.S. National Championships and the second Grand Slam tournament of the year.
See main article: 1904 U.S. National Championships – Men's singles. 
Holcombe Ward (USA) defeated William Clothier (USA) 10–8, 6–4, 9–7
See main article: 1904 U.S. National Championships – Women's singles. May Sutton (USA) defeated Elisabeth Moore (USA) 6–1, 6–2
Holcombe Ward (USA) / Beals Wright (USA) defeated Kreigh Collins (USA) / Raymond Little (USA) 1–6, 6–2, 3–6, 6–4, 6–1
May Sutton (USA) / Miriam Hall (USA) defeated Elisabeth Moore (USA) / Carrie Neely (USA) 3–6, 6–3, 6–3
Elisabeth Moore (USA) / Wylie Grant (USA) defeated May Sutton (USA) / Trevanion Dallas (USA) 6–2, 6–1