Created in 1924, Fort Matanzas National Monument is a United States National Monument run by the National Park Service. The Monument consists of a 1740 Spanish fort, Fort Matanzas, and about 100 acres (0.4 km²) of salt marsh and barrier islands along the Matanzas River on the northern Atlantic coast of Florida. It is operated by the Park Service in conjunction with the Castillo de San Marcos and several sites in the city of St. Augustine.

The Fort is accessible only by guided boat tours. Hiking trails are available on the barrier island.