The 1923 U.S. National Championships (now known as the US Open) was a tennis tournament that took place on the outdoor grass courts at the Germantown Cricket Club in Philadelphia, Pennsylvania, United States. The women's tournament was held from August 13 until August 18 while the men's tournament ran from September 10 until September 15. It was the 43rd staging of the U.S. National Championships and the third Grand Slam tennis event of the year.