Marvin S. Lachman (1932–2023) was an American mystery writer, editor, critic, and historian of mystery fandom. He co-authored and co-edited the Edgar Award-winning Encyclopedia of Mystery and Detection and wrote reference works on mystery fiction and its readership. His later books included The Heirs of Anthony Boucher: A History of Mystery Fandom and The Villainous Stage, a study of crime plays.

Lachman contributed articles, reviews, and columns to mystery journals, including a long-running column for Deadly Pleasures. He received the Mystery Writers of America’s Raven Award in 1997 for contributions outside creative writing.