| 1900 U.S. National Championships | |
|---|---|
| Date | August 13–21 (M) June 19–23 (W) |
| Edition | 20th |
| Category | Grand Slam |
| Surface | Grass |
| Location | Newport, R.I., United States (M) Philadelphia, PA, United States (W) |
| Champions | |
| Men's singles | |
 Malcolm Whitman[1] | |
| Women's singles | |
| Myrtle McAteer[1] | |
| Men's doubles | |
| Holcombe Ward / Dwight Davis[1] | |
| Women's doubles | |
| Hallie Champlin / Edith Parker[1] | |
| Mixed doubles | |
| Margaret Hunnewell / Alfred Codman[1] | |
List of champions of the 1900 U.S. National Championships tennis tournament (now known as the US Open). The men's tournament was held from August 13 to August 21 on the outdoor grass courts at the Newport Casino in Newport, Rhode Island. The women's tournament was held from June 19 to June 23 on the outdoor grass courts at the Philadelphia Cricket Club in Philadelphia, Pennsylvania. It was the 20th U.S. National Championships and the second Grand Slam tournament of the year.