Evelyn C. Leeper is an American writer, critic, and active member of science fiction fandom.
She was a member and officer of the UMass Science Fiction Society from 1968 to 1972. In 1978 she and her husband Mark founded the Science Fiction Club at Bell Labs.
She and Mark have been Fan Guests of Honor at Novacon (1973, Michigan); Covert Contraption (1989, Michigan); and Windycon XXIX (2002, Chicago).
She and Mark have co-edited/co-published their weekly fanzine (the MT VOID) since 1978. As of July 15, 2016, it has had 1919 issues.
She was one of the judges of the Sidewise Award for Alternate History from 1995 to 2014 and a contributor to Uchronia: The Alternate History List. She has been nominated for the Hugo Award for Best Fan Writer twelve times (1990-2001), losing on each occasion to David Langford.