Edgartown is a town on the island of Martha's Vineyard in Dukes County, Massachusetts, United States, for which it is the county seat. The town's population was 5,168 at the 2020 census. It was once a major whaling port, with historic houses that have been carefully preserved. Today it hosts yachting events around its large harbor. Edgartown also includes Chappaquiddick Island, a peninsula accessible by ferry.