The Gunpowder River is a 6.8-mile-long (10.9 km) tidal inlet on the western side of the Chesapeake Bay in Maryland, United States. It is formed by the joining of two freshwater rivers, Gunpowder Falls and Little Gunpowder Falls.

Baltimore County is the third-most populous county in the U.S. state of Maryland. It is part of the Baltimore metropolitan area.