Selinsgrove is the largest borough in Snyder County, Pennsylvania, United States. The population is estimated to be 5,761 for the 2020 Census. Selinsgrove is geographically located in the middle of the Susquehanna River Valley in Central Pennsylvania, along U.S. Routes 11 and 15, 45 miles north of Harrisburg and 5.7 miles southwest of Sunbury. It is the home of Susquehanna University.