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).^[1] He was nicknamed "Chub", but was 6 feet tall and weighed a mere 164 pounds.^[1] During his career, he was a popular player, sometimes known as a clown for his antics, and an early pioneer of the slide.^[2]

Born in Boston, Massachusetts, Sullivan, as a 21-year-old rookie in 1877, was the tenth-youngest player to appear in a National League game during that season,^[3] replacing Charlie Gould at first base.^[4] Joining the team late in the season, he played in only eight games, and batted .250.^[1] He stayed on with the Reds for the 1878 season, leading the league in games played, assists by a first baseman, and fielding percentage (.975).^[1] A tough hitter to strike out, Chub also finished seventh in at bat to strikeout ratio (27.1 to 1).^[3]

Sullivan joined the Worcester minor league club for the 1879 season,^[2] and the team did very well in a championship tournament following the season, and decided to apply as a replacement team in the National League, when the Syracuse Stars folded following the 1879 season. The team was accepted, and joined the League for the 1880 season.^[5] Sullivan played in 43 games, the last season of his career, batted .259, and is credited with zero RBIs.^[1] Sullivan's career totals include 112 games played, 114 hits, 55 runs scored, 24 RBIs, and a batting average of .258.^[1]

Sullivan became ill before the next season began, and eventually died on September 12 in his hometown of Boston, Massachusetts at the age of 25^[1] of consumption, later known as tuberculosis.^[6] His Worcester teammates wore a black crêpe on their jersey sleeves in his memory, for the 1881 season.^[7]