The 1966 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 11 September. It was the 86th staging of the U.S. National Championships, and the fourth Grand Slam tennis event of 1966.

Finals

Men's singles

🇦🇺 Fred Stolle defeated 🇦🇺 John Newcombe 4–6, 12–10, 6–3, 6–4

Women's singles

🇧🇷 Maria Bueno defeated 🇺🇸 Nancy Richey 6–3, 6–1

Men's doubles

🇦🇺 Roy Emerson / 🇦🇺 Fred Stolle defeated 🇺🇸 Clark Graebner / 🇺🇸 Dennis Ralston 6–4, 6–4, 6–4

Women's doubles

🇧🇷 Maria Bueno / 🇺🇸 Nancy Richey defeated 🇺🇸 Rosie Casals / 🇺🇸 Billie Jean King 6–3, 6–4

Mixed doubles

🇺🇸 Donna Floyd-Fales / 🇦🇺 Owen Davidson defeated 🇺🇸 Carol Hanks Aucamp / 🇺🇸 Ed Rubinoff 6–1, 6–3