Cliff Eisen (born in Toronto, 21 January 1952) is a Canadian musicologist and a Mozart expert. He has been based, since 1997, in the Department of Music at King's College London. As part of the Department's strong connections with the Royal Academy of Music, Eisen also leads courses there. He has studied at the University of Toronto and at Cornell University, and has taught at the University of Western Ontario and New York University.
Eisen is associate editor of the new Köchel catalogue and received the Alfred Einstein Award of the American Musicological Society in 1992. His research focuses on the Classical period, particularly Mozart and performance practice. He has written extensively on the issues of authenticity surrounding the works of Leopold Mozart and his son, Wolfgang. Other publications of his deal with Mozart's chamber music, life in Salzburg, biography and his life in contemporary documentation.