Mary O'Hara Alsop (July 10, 1885 – October 14, 1980) was an American author, screenwriter, pianist, and composer best known for the novel My Friend Flicka.

O'Hara was a Hollywood screenwriter for silent era films that include The Prisoner of Zenda (1922), Braveheart (1925), and Framed (1927).

In 1961, she performed her folk musical composition The Catch Colt at the Catholic University of America, Washington, D.C. She was the author of several books including Let Us Say Grace (1930), My Friend Flicka (1941), and Novel-in-the-Making (1954). She died from arteriosclerosis on October 14, 1980, in Chevy Chase, Maryland.