Bush River is a tidal estuary in Harford County, Maryland, located about 15 mi (24 km) northeast of Baltimore. The estuary extends southward from the community of Riverside for about 9 mi (14 km) to Chesapeake Bay. The watershed area of tidal Bush River is 125 mi<sup>2</sup> (320 km<sup>2</sup>), and includes Aberdeen Proving Ground, a military facility.
Bush River has three principal tributaries: Bush Creek, Church Creek and Otter Point Creek. The smaller tributaries are: