The 1965 U.S. National Championships (now known as the US Open) was a tennis tournament that took place on the outdoor grass courts at the West Side Tennis Club, Forest Hills in New York City, United States.

The tournament ran from 1 September until 12 September.

It was the 85th staging of the U.S. National Championships, and the fourth Grand Slam tennis event of 1965.

Manuel Santana defeated Cliff Drysdale 6–2, 7–9, 7–5, 6–1 Margaret Smith defeated Billie Jean Moffitt 8–6, 7–5 Roy Emerson / Fred Stolle defeated Frank Froehling / Charles Pasarell 6–4, 10–12, 7–5, 6–3 Carole Graebner / Nancy Richey defeated Billie Jean Moffitt / Karen Susman 6–4, 6–4 Margaret Smith / Fred Stolle defeated Judy Tegart / Frank Froehling 6–2, 6–2