John Patrick Campbell (b. Belfast, 7 March 1883; d. New York, 19 August 1962) was an illustrator, caricaturist, political cartoonist, watercolourist and theatre designer from Belfast who often signed his work as Seaghan MacCathmhaoil. He was the brother of the poet Joseph Campbell. He drew cartoons and caricatures for Nomad's Weekly (1904, 1908-1911), Bulmer Hobson's The Republic (1907) and The New Age (1909), and contributed drawings and cover designs to Ulad (1904-1905), and The Shanachie (1906).