Bush Mill Stream Natural Area Preserve is a 144-acre protected area in Northumberland County, Virginia, where freshwater Bush Mill Stream meets the saltwater Great Wicomico River. Its fresh and brackish tidal wetlands form a transition zone that provides important habitat for numerous bird species. Open to the public during daylight hours, the preserve offers trails, a boardwalk over the stream, and an observation deck that give access to the wetlands. The Virginia Department of Conservation and Recreation owns and maintains the preserve.