Foster is a small unincorporated community in Mound Township, Warren County, in the U.S. state of Indiana. As of the 2020 census, Foster had a population of 104.
Foster was platted on April 25, 1893, on land donated by William R. Foster, an early settler. At one time the town had a post office, blacksmith shop, railroad depot, two stores, a stockyard, a threshing machine, a grain elevator and a sawmill. Currently it consists of a few private residences, a couple of small shops and a motel.
A post office was established at Foster in 1883, and remained in operation until it was discontinued in 1905.
Foster is located just north of U.S. Route 136 about west of Covington and about east of the Indiana-Illinois border. The Vermilion Valley Railroad (originally the New York Central Railroad) passes through Fowler, and the north fork of Spring Creek flows along its western edge.
It is in the Covington Community School Corporation.