John Frank "Chub" Sullivan (January 12, 1856 – September 12, 1881) was an American Major League Baseball first baseman who played for three seasons: two with the Cincinnati Reds (1877–1878) and one with the Worcester Worcesters (1880). He was nicknamed "Chub", but was 6 feet tall and weighed a mere 164 pounds. During his career, he was a popular player, sometimes known as a clown for his antics, and an early pioneer of the slide.