St. Petersburg is a city in Pinellas County, Florida, United States. As of the 2015 census estimate, the population was 257,083, making it the fifth-most populous city in Florida and the largest in the state that is not a county seat (the city of Clearwater is the seat of Pinellas County).
As of the 2017 census, the population of St. Petersburg Florida was 257,083.
St. Petersburg is the largest in the state that is a county seat.