Montana Highway 81

Highway 81 in the U.S. State of Montana is a route running in an easterly direction from an intersection with Montana Highway 80, north of the hamlet of Arrow Creek. The highway extends approximately 42 miles (68 km) to an intersection with U.S. Route 191 at the post office of Brooks. The landscape traversed by Highway 81 is uneven and largely rural, used mainly for agriculture and livestock grazing. For much of its length, the highway is roughly paralleled by the main line of Central Montana Rail, which is headquartered in Denton.

Before receiving its current designation, Highway 81 was designated as Montana Secondary Highway 235.