the 1938 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, united states. the tournament was scheduled to be held from thursday 8 september until saturday 17 september but was prolonged until saturday 24 september due to poor weather caused by the 1938 new england hurricane. it was the 58th staging of the u.s. national championships and the fourth grand slam tennis event of the year.