Pennsylvania Route 331 (PA 331), also known as Brush Run Road, is an 12-mile (19 km) long, east–west state highway located in Washington county in Pennsylvania. The western terminus is at the West Virginia state line in Independence Township. The eastern terminus is at PA 844 in Canton Township.

PA 331 begins at the West Virginia state border, at the eastern terminus of WV 67. The route primarily winds its way east from Independence Township to Canton Township. In the village of Acheson, PA 231 forms a short concurrency with PA 331. Its eastern terminus with PA 844 is 2 miles (3.2 km) southeast of the village of Buffalo.

The route was first signed in 1935, and has stayed on the same roads since its inception.