John Tomlinson Brush (June 15, 1845 – November 26, 1912) was an American sports executive who is primarily remembered as the owner of the New York Giants Major League Baseball franchise from 1890 until his death. He also owned the Indianapolis Hoosiers in the late 1880s, and the Cincinnati Reds from 1891 to 1902. Under his leadership, the Giants were revived as a franchise after a decline during the 1890s. Brush was also a leader in the formation of the rules that govern the modern World Series. He was one of 11 executives honored by the Baseball Hall of Fame on a Roll of Honor in 1946.
Born in Clintonville, New York, Brush was orphaned at age 4 and was raised by his grandfather until he left to enter business college at age 17. During the Civil War he enlisted in the First New York Artillery in 1863, and after the war's end he went into business running clothing stores in Albany, Troy and Lockport, New York. He moved to Indianapolis in 1875, eventually opening a department store, and became involved in local baseball as a means of promoting his store. He built a ballpark in 1882, and it became home to the Indianapolis Hoosiers of the American Association for their only major league season in 1884; they played in the Western League before that circuit folded after the 1885 campaign.
When the National League put the St. Louis Maroons franchise up for sale after the 1886 season, Brush bought it and relocated the team to Indianapolis. He renovated his ballpark, adding a special celebrity box which attracted such figures as President Benjamin Harrison, poet James Whitcomb Riley, and future novelist Booth Tarkington. In 1888 he offered a tryout to Bud Fowler, but ultimately decided not to challenge the sport's color line. Brush also devised a salary scale system which was designed to curtail player salaries, a move which helped contribute to the breakaway Players' League in 1890.