Bartholomew County is a county located in the U.S. state of Indiana. The population was 82,208 at the 2020 census. The county seat is Columbus. The county was determined by the U.S. Census Bureau to be home to the mean center of U.S. population in 1900. Bartholomew County makes up the Columbus, Indiana Metropolitan Statistical Area, which is part of the Indianapolis-Carmel-Muncie Combined Statistical Area.