St. Petersburg is a city in Pinellas County, Florida, United States. As of the 2018 census estimate, the population was 265,098, 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).

St. Petersburg is the fifth largest city in Florida and the second-largest city in the Tampa Bay Area, after Tampa. Together with Clearwater, these cities comprise the Tampa–St. Petersburg–Clearwater Metropolitan Statistical Area, the second-largest in Florida with a population of around 2.8 million. St. Petersburg is located on the Pinellas peninsula between Tampa Bay and the Gulf of Mexico, and is connected to mainland Florida to the north.

St. Petersburg was founded in 1888 by John C. Williams, who purchased the land, and by Peter Demens, who brought the railroad industry into the area. As a part of a coin toss bet, the winner, Peter Demens, named the land after Saint Petersburg, Russia, while Williams opted to name the first hotel built which was named the Detroit Hotel, both named after their home towns respectively. St. Petersburg was incorporated as a town on February 29, 1892 and re-incorporated as a city on June 6, 1903.

The city is often referred to by locals as St. Pete. Neighboring St. Pete Beach formally shortened its name in 1994 after a vote by its residents. St. Petersburg is governed by a mayor and city council.

With an average of some 361 days of sunshine each year, and a Guinness World Record for logging the most consecutive days of sunshine (768 days between 1967 and 1969), it is nicknamed “The Sunshine City”. Due to its good weather and low cost of living, the city has long been a popular retirement destination, although in recent years the population has moved in a much more youthful direction.American Style magazine ranked St. Petersburg its top mid-size city in 2011, citing its “vibrant” arts scene.