Mary Aline Langdon McDermott (October 23, 1881 – February 16, 1951) was an American actress.

She created the role of Mrs. Lily Mortar in the original Broadway production of Lillian Hellman's The Children's Hour (1934).

She was also in the original Broadway cast of Thornton Wilder's Our Town (1938).

Her Broadway credits included roles in The Runaway (1911),[2] Go West, Young Man (1923),[3][4] Bachelors' Brides (1925), American Born (1925),[5][6] The Rhapsody (1930), Page Pygmalion (1932),[7] The Children's Hour (1934–1936),[8] Our Town (1938), Blind Alley (1940), and State of the Union (1945–1947).

[1] She was a leading lady in touring and stock companies including the Northampton Players,[10][11] and was known for counseling young women away from a stage career.