The 1919 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 women's tournament was held from 16 June until 20 June while the men's tournament ran from 26 August until 4 September. It was the 39th staging of the U.S. National Championships and the second Grand Slam tennis event of the year.