Warren County is a county in the U.S. state of Indiana. It lies in the western part of the state between the Illinois state line and the Wabash River. According to the 2020 census, it had a population of 8,440. Its county seat is Williamsport.

Williamsport is a town in Washington Township, Warren County, in the U.S. state of Indiana. The population was 1,898 at the 2010 census. It is the county seat of Warren County and is the largest of the four incorporated towns in the county. Williamsport Falls is located in downtown Williamsport.