Fort Clinch, Coastal fortification in Nassau County, United States.

Fort Clinch is a pentagonal masonry fort begun in 1847 on the northern tip of Amelia Island, built of almost five million bricks. Its outer walls carry corner bastions and embrasures, and a two-story barracks stands in the interior courtyard. It belongs to the Third System of seacoast defense and lies within Fort Clinch State Park.

The Spanish first fortified this site in 1736. The United States began building Fort Clinch in 1847 as part of its Third System of coastal defense, naming it after General Duncan Lamont Clinch following his death in 1849. Confederate forces seized it in early 1861 and used it for blockade runners; in March 1862 Robert E. Lee ordered it abandoned, after which Union troops held it as a base for operations along the Georgia and Florida coasts.

Fort Clinch runs a living history program in which reenactors in 1860s clothing portray people who lived at the fort, and visitors can talk with them. On the first weekend of every month, a soldier garrison fires cannons and demonstrates other battlefield skills.

Fort Clinch is open year-round from 8:00am until sundown, and the site lies northeast of Fernandina Beach at the entrance to Cumberland Sound, inside Fort Clinch State Park. Expect brick ramps, stairs and uneven ground between the inner and outer walls, the corner bastions and the two-story barracks.

The fort's walls required almost five million bricks, and construction began in 1847 as part of the Third System of coastal defense. The site had been fortified since 1736 by the Spanish, and later by other nations, to guard the entrance to the St. Marys River and Cumberland Sound.