Ithaca is a city and the county seat of Gratiot County, Michigan. It is located very near the geographical center of the state's lower peninsula. The population was 2,910 at the 2010 census. Ithaca is run as a council-manager government. It sits at the conjunction of four townships in the center of the county: Emerson Township to the northeast, Arcada Township to the northwest, Newark Township to the southwest, and North Star Township to the southeast, but is administratively autonomous.

Gratiot County is a county in the U.S. state of Michigan. As of the 2020 Census, the population was 41,761. The county seat is Ithaca, although its most populous city is Alma.