The 1948 U.S. National Championships (now known as the US Open) was a tennis tournament that took place on the outdoor grass courts in the United States. The men's and women's singles events as well as the mixed doubles were held at the West Side Tennis Club, Forest Hills in New York City, while the men's and women's doubles events were played at the Longwood Cricket Club in Chestnut Hill, Massachusetts. The tournament ran from September 10 until September 19. It was the 68th staging of the U.S. National Championships, and the fourth Grand Slam tennis event of the year. Pancho Gonzales and Margaret Osborne duPont won the singles titles.

Finals

Men's singles

🇺🇸 Pancho Gonzales defeated Eric Sturgess 6–2, 6–3, 14–12

Women's singles

🇺🇸 Margaret Osborne duPont defeated 🇺🇸 Louise Brough 4–6, 6–4, 15–13

Men's doubles

🇺🇸 Gardnar Mulloy / 🇺🇸 Bill Talbert defeated 🇺🇸 Frank Parker / 🇺🇸 Ted Schroeder 1–6, 9–7, 6–3, 3–6, 9–7

Women's doubles

🇺🇸 Louise Brough / 🇺🇸 Margaret Osborne duPont defeated 🇺🇸 Patricia Todd / 🇺🇸 Doris Hart 6–4, 8–10, 6–1

Mixed doubles

🇺🇸 Louise Brough / 🇺🇸 Tom Brown defeated 🇺🇸 Margaret Osborne duPont / 🇺🇸 Bill Talbert 6–4, 6–4