1940 U.S. National Championships (tennis)

The 1940 U.S. National Championships was a tennis tournament held at the West Side Tennis Club in Forest Hills, New York City. It ran from August 29 to September 8. It was the 60th edition of the U.S. National Championships and the fourth Grand Slam tournament of the year. Don McNeill defeated Bobby Riggs in the men's singles final, and Alice Marble defeated Helen Jacobs in the women's singles final. The men's doubles title was won by Jack Kramer and Ted Schroeder, who defeated Gardnar Mulloy and Henry Prusoff. The women's doubles title was won by Sarah Palfrey Cooke and Alice Marble, who defeated Dorothy Bundy and Marjorie Gladman Van Ryn. The mixed doubles title was won by Alice Marble and Bobby Riggs, who defeated Dorothy Bundy and Henry Prusoff. This tournament was notable for being held during the early stages of World War II, which significantly impacted international participation in subsequent years.