The St. Lucie River is a 35-mile-long (56 km) estuary linked to a coastal river system in St. Lucie and Martin counties in the U.S. state of Florida. The St. Lucie River and St. Lucie Estuary are an "ecological jewel" of the Treasure Coast, central to the health and well-being of the surrounding communities. The river is part of the larger Indian River Lagoon system, the most diverse estuarine environment in North America with more than 4,000 plant and animal species, including manatees, oysters, dolphins, sea turtles and seahorses.

St. Lucie County is located in the southeastern portion of the U.S. state of Florida. As of the 2020 census, the population was 329,226. The county's seat is Fort Pierce, while the largest city is Port St. Lucie, making up 62% of the county's population. St. Lucie County is the principal county of the Port St. Lucie, FL Metropolitan Statistical Area.