Frederick Charles "Fritz" Koster (December 21, 1905 – April 24, 1979) was born December 21, 1905 in Louisville, Kentucky. He was an outfielder in Major League Baseball who played for the Philadelphia Phillies during the 1931 season.
Koster attended the University of Louisville, where he played college baseball for the Cardinals from 1926 to 1928.
Koster died in St. Matthews, Kentucky and was buried in Cave Hill Cemetery in Louisville.