F.J. McMahon was an American singer-songwriter known for his lone 1969 album Spirit of the Golden Juice, a cult classic in the genre of psychedelic folk. A U.S. Air Force veteran, McMahon drew inspiration from his experiences during the Vietnam War era, blending introspective lyrics with simple, evocative acoustic arrangements. Though largely overlooked at the time of its release, his work later gained recognition among collectors and folk enthusiasts for its raw, sincere expression and has since been reissued to critical acclaim.