Marshfield is a town in Plymouth County, Massachusetts, United States, on Massachusetts's South Shore. The population was 25,825 at the 2020 census.

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.