Plymouth is a town and county seat of Plymouth County, Massachusetts, United States. Located in Greater Boston, the town holds a place of great prominence in American history, folklore, and culture, and is known as "America's Hometown". Plymouth was the site of the colony founded in 1620 by the Mayflower Pilgrims, where New England was first established. It is the oldest municipality in New England and one of the oldest in the United States. The town has served as the location of several prominent events, one of the more notable being the First Thanksgiving feast. Plymouth served as the capital of Plymouth Colony from its founding in 1620 until the colony's merger with the Massachusetts Bay Colony in 1691. The English explorer John Smith named the area Plymouth and the region 'New England' during his voyage of 1614. It was a later coincidence that, after an aborted attempt to make the 1620 trans-Atlantic crossing from Southampton, the Mayflower finally set sail for America from Plymouth, England.

Plymouth County is a county in the U.S. state of Massachusetts, south of Boston. As of the 2020 census, the population was 530,819. Its county seats are Plymouth and Brockton. In 1685, the county was created by the Plymouth General Court, the legislature of Plymouth Colony, predating its annexation by the Massachusetts Bay Colony.