Mary Lou Foy (born August 17, 1944) is an American photojournalist. She served as Picture Editor at the Washington Post from 1990 to 2006 and was president of the National Press Photographers Association in 1992.
Foy attended Auburn High School and Auburn University, receiving a B.A. in journalism from the latter in 1966. She attended graduate school at the University of Florida in journalism and environmental engineering, and in 1971 became the first female photojournalist to work for the Gainesville Sun. In 1974, she joined the staff of the Fort Lauderdale Sun-Sentinel, and in 1976 became the first woman photojournalist on the staff of the Miami Herald.
Foy rose from that position to become Picture Editor of the Herald, before being hired by the Washington Post in 1990 as National/Style Picture Editor. She served in that position at the Post until 2006. Foy served as secretary of the National Press Photographers Association in 1984 and 1985, vice president in 1991, and president of that organization in 1992. She received the Samuel Mellor Award in 1984, the Joseph Costa Award in 1998, the Morris Berman NPPA Citation in 2003, and twice received the NPPA's President's Award in 1984 and 1986.