Westmoreland County is a county located in the Northern Neck of the Commonwealth of Virginia. As of the 2020 census, the population sits at 18,477. Its county seat is Montross.

The Northern Neck is the northernmost of three peninsulas on the western shore of the Chesapeake Bay in the Commonwealth of Virginia(along with the Middle Peninsula and the Virginia Peninsula). The Potomac River forms the northern boundary of the peninsula; the Rappahannock River demarcates it on the south. The land between these rivers was formed into Northumberland County in 1648, prior to the creation of Westmoreland County and Lancaster County.