Stuart is a city in and the county seat of Martin County, Florida, United States. Located in southeastern Florida, Stuart is the largest of five incorporated municipalities in Martin County. The population is 17,425 according to the 2020 U.S. census. Stuart is the 126th largest city in Florida based on official 2019 estimates from the U.S. Census Bureau. It is part of the Port St. Lucie, Florida Metropolitan Statistical Area.