The 1927 U.S. National Championships was a tennis tournament that took place on the outdoor grass courts at the West Side Tennis Club, Forest Hills in New York City, New York. The women's tournament was held from August 22 until August 30 while the men's tournament ran from September 12 until September 17. It was the 47th staging of the U.S. National Championships and the fourth Grand Slam tennis event of the year. This edition saw the introduction of seedings in the draw which were meant to prevent the best players from meeting each other in the early rounds of the tournament.