John McDermott, also known under the pen names J.M. Ryan and Mariner, was an American illustrator and author noted for action and adventure illustrations.
McDermott worked as an in-between and effects animator for Walt Disney Studios and as a US Marine combat artist, before establishing himself as a cover illustrator for 1950s paperbacks and pulp magazines such as Argosy, American Weekly, and Outdoor Life. Under his J.M. Ryan pen name, he wrote the novels The Rat Factory (1971), a derogatory satire of Walt Disney and the Disney studio; Brooks Wilson Ltd (1967), on which the 1970 film Loving was based; and Mother's Day (1969) about Ma Barker. Under his own name, he novelized director-writer Bo Widerberg's screenplay for the 1971 film Joe Hill, which would be his final published book.
