Capitol Park (I), was a baseball field in Washington, D.C.

The grounds were the home field for the Washington Nationals of the Union Association during the league's only season in 1884.

[1] The ballpark had a seating capacity of 6,000, and was where the Russell Senate Office Building stands today.

After dropping out of the Union Association, the club joined the minor Eastern League for the 1885 season.

The club regrouped as a new entry to the National League in 1886, and moved a few blocks north to the larger Capitol Park (II).