1921 U.S. National Championships (tennis)
| 1921 U.S. National Championships | |
|---|---|
| Date | September 9–19 (M) August 15–20 (W) |
| Edition | 41st |
| Category | Grand Slam (ITF) |
| Surface | Grass |
| Location | Philadelphia, Pennsylvania, US (MS) Forest Hills, New York, US (WS, WD) Chestnut Hill, Massachusetts (MD, XD) |
| Venue | Germantown Cricket Club (MS) West Side Tennis Club (WS, WD) Longwood Cricket Club (MD, XD) |
| Champions | |
| Men's singles | |
| Bill Tilden | |
| Women's singles | |
| Molla Bjurstedt Mallory | |
| Men's doubles | |
| Bill Tilden / Vincent Richards | |
| Women's doubles | |
| Mary Browne / Louise Riddell Williams | |
| Mixed doubles | |
| Mary Browne / Bill Johnston | |
The 1921 U.S. National Championships (now known as the US Open) was a tennis tournament that took place on the outdoor grass courts at three locations in the United States. The men's singles event was held from September 9 until September 19 at the Germantown Cricket Club in Philadelphia, while the women's singles and doubles events were held from August 15 until August 20 at the West Side Tennis Club in Forest Hills, New York. The men's and mixed doubles competitions took place at Longwood Cricket Club in Chestnut Hill, Massachusetts. It was the 41st staging of the U.S. National Championships and the second Grand Slam tennis event of the year.
Although Molla Bjurstedt Mallory won the women's singles event for the sixth time in seven years, her victory was overshadowed by her second-round win over Suzanne Lenglen, who was making her only ever competitive appearance in the United States. Lenglen retired from the match after losing the first set, the only competitive loss of her career after World War I.