Mary Stevenson, known professionally as Mary Gannon, was an American actress who had an active stage career in comedies and vaudeville during the mid 19th century. A gifted comedienne, she became associated with many of the matron roles of 18th and 19th century comedies. Shortly before her death at the age of 39, New York theatre critic Joseph N. Ireland wrote of Gannon, "[she] is now universally acknowledged to be the best general comic actress in the city."