Keystone Heights is a city located in southwestern Clay County, Florida, United States. It is the southwestern most city in the Jacksonville, Florida Metropolitan Statistical Area, and is the principal city and primary economic driver of the Lake Region, a region in Florida consisting of southwestern Clay County and parts of Bradford, Putnam, and Alachua counties, known for its many lakes. The city's name is derived from the state of Pennsylvania's nickname, the "Keystone State".