Fort Brown, Military fort and historic district in Brownsville, United States.

Fort Brown began in 1846 as a star-shaped earthwork for 800 men, laid out by Captain Joseph K. Mansfield on the north bank of the Rio Grande. Its surviving elements form a discontiguous National Historic Landmark District: the 1846 earthworks, an 1848 cavalry barracks, and buildings raised mainly between 1868 and 1870, among them a hospital, morgue, barracks, commissary, colonel's house and officers' quarters.

Established in 1846 during the Mexican-American War, the post was named after Major Jacob Brown who died in battle there. Most of the stone structures visitors see today were built in the years following the war, between 1868 and 1870.

The fort's name comes from Major Jacob Brown, killed during the 1847 siege of Fort Texas; General Zachary Taylor renamed the post in his honour. The nearby city of Brownsville, founded in 1849, took its name from the same fort. The surviving 1848 cavalry barracks and the 1868–1870 buildings now belong to Texas Southmost College.

The site is straightforward to explore on foot since the main buildings are grouped together and clearly marked. Wear comfortable shoes as you will walk quite a bit to see both the earthworks and all the structures spread across the grounds.

On April 20, 1915, Signal Corps officers Byron Q. Jones and Thomas Millings flew a Martin T over the fort for 20 minutes at 2,600 feet to spot Pancho Villa's movements. The plane did not cross into Mexico, but was fired on by machine guns and small arms; such patrols continued for six weeks.