Stuart is a city in and the seat of Martin County, Florida, United States. Located on Florida's Treasure Coast, Stuart is the largest of four incorporated municipalities in Martin County. The population is 17,425 according to the 2020 United States Census. Stuart is the 126th largest city in Florida based on official 2019 estimates from the US Census Bureau. It is part of the Port St. Lucie, Florida Metropolitan Statistical Area. Stuart is frequently cited as one of the best small towns to visit in the U.S., in large part because of its proximity to the St. Lucie River and Indian River Lagoon.