Marie Wagner (February 2, 1883 – April 1, 1975[1] or March 28, 1975[2]) was an American tennis champion.

An outstanding tennis player, she won the United States Indoor Championships a record number of times.

In the singles event, she won the title six times (1908, 1909, 1911, 1913, 1914, and 1917) while in doubles, she was successful in 1910, 1913 (with Clara Kutross), 1916 (with Molla Mallory) and in 1917 (with Margaret Taylor).

[1] At the U.S. National Championships, her best showing was reaching the final in 1914 which she lost in three sets to reigning champion Mary Browne.

When Harpo was a child, the Marx family lived in a tenement building at 179 93rd Street, New York, New York, across the street from Wagner's brownstone.