Watson Brake, Prehistoric mound complex in Ouachita Parish, United States.

Watson Brake is a prehistoric archaeological site in northern Louisiana consisting of eleven earthen mounds connected by ridges that form an oval pattern approximately 275 meters (900 feet) in diameter. The mounds rise between 1.2 and 7.6 meters (4 and 25 feet) above the surrounding terrain and are positioned in an arrangement that encloses a central open area.

Occupation began around 4000 BCE; mound building started about 3500 BCE and continued roughly 500 years, with Mound A raised in at least seven layers separated by soil horizons. In the early 1980s local resident Reca Bamburg Jones identified eleven mounds linked by ridges after logging exposed them, and Joe W. Saunders's team published radiocarbon dates in Science in 1997.

The name combines that of a former landowner, Watson, with an Old English word for fallow land, and it was given to the watercourse beside the mounds. The builders were mobile hunter-gatherers, not farmers: midden remains show they ate fish, shellfish, deer and goosefoot, and stored no provisions. The connecting ridges contain debris from food preparation, including cracked cooking stones and fired clay objects.

The site is closed to the public: about half is still held by Gentry family members, who permit excavations but not viewing, and the other half is state-owned for preservation. It lies south of Monroe near Watson Bayou, on a terrace above the Ouachita River, reached only by arrangement with the owners or the state. The mounds and connecting ridges stand in open, grassy ground, with a stream and forest beyond.

Researchers have found that construction activity at the site coincided with El Niño climate events, suggesting that environmental conditions influenced building efforts. This correlation sheds light on the close connection between early societies and the climatic conditions of their surroundings.