Chatham County is located in the U.S. state of Georgia, on the state's Atlantic coast. The county seat and largest city is Savannah. One of the original counties of Georgia, Chatham County was created February 5, 1777, and is named after William Pitt, 1st Earl of Chatham.

Savannah is the oldest city in the U.S. state of Georgia and the county seat of Chatham County. Established in 1733 on the Savannah River, the city of Savannah became the British colonial capital of the Province of Georgia and later the first state capital of Georgia. A strategic port city in the American Revolution and during the American Civil War, Savannah is today an industrial center and an important Atlantic seaport. It is Georgia's fifth most populous city, with a 2020 U.S. census population of 147,780. The Savannah metropolitan area, Georgia's third-largest, had a 2020 population of 404,798.