Onancock is a town in Accomack County, Virginia, United States. The population was 1,263 at the 2010 census.

Accomack County is a United States county located in the eastern edge of the Commonwealth of Virginia. Together, Accomack and Northampton counties make up the Eastern Shore of Virginia, which in turn is part of the Delmarva Peninsula, bordered by the Chesapeake Bay and the Atlantic Ocean. Accomac is the county seat.