Guana Tolomato Matanzas National Estuarine Research Reserve (GTM Research Reserve) is dedicated to the conservation of natural biodiversity and cultural resources through research and monitoring to guide science-based stewardship and education strategies.

GTM Research Reserve protects 76,760 acres south of the city of Jacksonville (Duval County), in St. Johns and Flagler counties on the northeast coast of Florida, one of the fastest-growing regions in the state. These protected areas provide a habitat for a variety of fish and wildlife. A species list recently compiled for Guana River Marsh Aquatic Preserve indicated the presence of at least 44 mammals, 358 birds, 41 reptiles, 21 amphibia, 303 fish, and 580 plants. The research reserve contains habitats essential to 48 protected animals and eight protected plants. GTM Research Reserve is important for the economy because these include 16 species that are fished or harvested commercially and 18 species that are fished recreationally.

The GTM Research Reserve encompasses many parcels of land and water that are protected for conservation. It is named for the three rivers that tie these parcels together: Guana River, Tolomato River, and Matanzas River.

Encompassing almost 74,000 acres of estuary and uplands, the reserve offers nearly 10 miles of trails for walking, hiking, biking, horseback riding, dog walking, nature viewing, and picnicking. Horses and leashed pets are allowed on the Guana Ponte Vedra Beach trails. Dogs are allowed on the trail at Marineland.