Jeff Simmons, born May 1949 in Seattle, Washington, is a rock musician and former member of Frank Zappa's Mothers of Invention. Simmons provided bass, guitar, vocals and harmonica for the group between 1970 and 1971. He left The Mothers just prior to the filming of 200 Motels (where he was replaced in the film by Ringo Starr's chauffeur Martin Lickert) in mid 1971. Jeff later returned to the group for a time during 1972 and 1973. Zappa and Mothers albums he appeared on include Chunga's Revenge (1970), Waka/Jawaka (1972), Roxy & Elsewhere (1974).

Years later Zappa released a number of archival recordings made during this period that feature Jeff including You Can't Do That on Stage Anymore, Vol. 1 (1988), You Can't Do That on Stage Anymore, Vol. 6 (1992), and Playground Psychotics (1992). Jeff also appears in the Zappa movie The True Story Of Frank Zappa's 200 Motels (1989). Numerous Zappa bootleg recordings from the same era also feature Simmons.