Plymouth is a village in Hancock and McDonough counties, Illinois, United States.

[5] A small portion of the village extends east into the southwest corner of McDonough County.

Carthage, the Hancock County seat, is 21 miles (34 km) to the northwest of Plymouth.

According to the 2021 census gazetteer files, Plymouth has a total area of 0.57 square miles (1.48 km2), all land.

Residents attend Southeastern High School which is located in nearby Augusta.