John Thaddeus Ostrowski (October 17, 1917 – November 13, 1992) was an American professional baseball player. Born in Chicago, he was an outfielder and third baseman who spent all or part of seven Major League seasons (1943–1946; 1948–1950) with the Chicago Cubs, Boston Red Sox, Chicago White Sox and Washington Senators. Listed at 5 feet 10+1⁄2 inches (1.791 m) tall and 170 pounds (77 kg), Ostrowski batted and threw right-handed.

Johnny Ostrowski
Left fielder / Third baseman
Born: (1917-10-17)October 17, 1917 Chicago, Illinois, U.S.
Died: November 13, 1992(1992-11-13) (aged 75) Chicago, Illinois, U.S.
Batted: Right Threw: Right
MLB debut
September 24, 1943, for the Chicago Cubs
Last MLB appearance
October 1, 1950, for the Chicago White Sox
MLB statistics
Batting average	.234
Home runs	14
Runs batted in	74
Teams
Chicago Cubs (1943–1946) Boston Red Sox (1948) Chicago White Sox (1949–1950) Washington Senators (1950)

Over his 216 MLB games played, Ostrowski was a .234 hitter (131-for-561) with 14 home runs and 74 RBI in 216 games, including 73 runs, 20 doubles, nine triples, seven stolen bases, and a .321 on-base percentage. However, in a 1,600-game minor league baseball career, Ostrowski hit 218 home runs and five times exceeded the 20-homer mark, including two 30 home run seasons.

Ostrowski died in Chicago at the age of 75.