Jim McWilliams (born February 10, 1937) is an American artist and graphic designer who was active as an avant-garde performer and composer during the 1960s and 1970s.

After 1966, McWilliams’s artworks and performances were often realized in collaboration with Moorman. He composed numerous works for her, including Ice Music (1972), in which she used a file, a saw, a long strip of plexiglass, and other tools to play a cello made of ice until it melted.