1900 U.S. National Championships (tennis)

1900 U.S. National Championships
DateAugust 13–21 (M)
June 19–23 (W)
Edition20th
CategoryGrand Slam
SurfaceGrass
LocationNewport, R.I., United States (M)
Philadelphia, PA, United States (W)
Champions
Men's singles
Malcolm Whitman
Women's singles
Myrtle McAteer
Men's doubles
Holcombe Ward / Dwight Davis
Women's doubles
Hallie Champlin / Edith Parker
Mixed doubles
Margaret Hunnewell / Alfred Codman

The 1900 U.S. National Championships (now known as the US Open) was a tennis tournament that took place in June and August of 1900. 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. 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. It was the 20th U.S. National Championships and the second Grand Slam tournament of the year.