Negro Fort was a short-lived fortification built by the British in 1814, during the War of 1812, in a remote part of what was at the time Spanish Florida. It was intended to support a never-realized British attack on the U.S. via its southwest border,: 22  by means of which they could "free all these Southern Countries [states] from the Yoke of the Americans".: 40  Built on a militarily significant site overlooking the Apalachicola River, it was the largest structure between St. Augustine and Pensacola.: 47  Trading posts of Panton, Leslie and Company and then John Forbes and Company, loyalists hostile to the United States, had existed since the late eighteenth century there and at the San Marcos fort, serving local Native Americans and fugitive slaves. The latter, having been enslaved on plantations in the American South, used their knowledge of farming and animal husbandry to set up farms stretching for miles along the river.

When withdrawing in 1815, at the end of the war, the British commander Edward Nicolls, intentionally left the fully-armed fort in the hands of his former Corps of Colonial Marines. The Corps was made up largely of free negroes and fugitive slaves. Also at the Fort were Creek and Choctaw allies who had served alongside the British during the war. As Nicolls hoped, the fort, near the Southern border of the United States, became a center and symbol of resistance to American slavery. It is the largest and best-known instance before the American Civil War in which armed fugitive slaves resisted white Americans who sought to return them to slavery. (A much smaller example was Fort Mose, near St. Augustine.)

The British did not name the fort. The name "negro fort" was coined by Indian Agent Benjamin Hawkins.: 76  The Creeks, who were there before Europeans arrived, had rights that enslaved Africans did not have. He led the calls for the fort's destruction.

The fort was destroyed in 1816, at the command of General Andrew Jackson, in the Battle of Negro Fort (also called the Battle of Prospect Bluff or the Battle of African Fort). The former slaves had not been trained in the use of the cannon and other heavy munitions, and they were thus unable to defend themselves. From a boat on the river, the American forces used red-hot shot, trying to start a fire. A shot landed in the powder magazine, which ignited, blowing up the fort and killing over 270 people instantly.

This is the only time in its history in which the United States destroyed a community of escaped slaves in another country.: 14  However, the area continued to attract escaped slaves until the U.S. construction of Fort Gadsden in 1818.

The Battle of Negro Fort was the first battle of the Seminole Wars.