Original Town of Fernandina Historic Site, Spanish colonial site in Nassau County, Florida.

The Original Town of Fernandina Historic Site, or Old Town, occupies a bluff above the Amelia River at the northwest end of Amelia Island. Its 1811 Spanish plat, based on the 1573 Law of the Indies, survives in the street grid and lot orientation. Plaza San Carlos, the former parade ground of Fort San Carlos, is now a state-maintained space for picnicking and nature study.

The Spanish platted Old Town in 1811 as the last Spanish city laid out in the Western Hemisphere, following the 1573 Law of the Indies. David Levy Yulee's railroad from Fernandina Beach to Cedar Key opened on March 1, 1861; he then platted new Fernandina along Centre Street, moving the town and leaving Old Town a residential neighborhood. The city marked the 200th anniversary of the founding on April 2, 2011.

The Timucua called Amelia Island Napoyca, and Spanish Franciscans had established the mission of Santa María de Sena near here by 1602, a league from San Pedro de Mocama on Cumberland Island. Plaza San Carlos, the ground before the vanished Fort San Carlos, is now kept by the Florida Department of Environmental Protection as part of the state park system, used for nature study and picnics.

Access to the site is through North 14th Street, with designated outdoor areas for exploration and recreation. Visitors should prepare for varying weather and seasonal conditions typical of Florida's coastal region.

Archaeological digs at the site reveal multiple layers of settlement from Native American times through French, Spanish, and British colonial periods. These buried layers tell the story of shifting control and occupation across several centuries.