State Route 13 (SR-13) is a 336-mile-long (541 km) state highway in the western part of the U.S. state of Alabama. Except for a portion roughly between Berry and Russellville, SR-13 is the unsigned designation for U.S. Highway 43. Thus, while the total distance of the route is over 330 miles (530 km), as an independently signed route, SR-13 is only 60 miles (97 km) long.

The southern terminus of SR-13 and US-43 is at their junction with U.S. Highway 90 and unsigned State Route 16 in Mobile. The northern terminus of the route is on US-43 at the Tennessee state line north of Killen in Lauderdale County. As a signed route, the southern terminus of the route is at the junction of US-43 and State Route 18 in southern Fayette County, and the northern terminus as at US-43 and State Route 17 south of Russellville in Franklin County.

East of Fayette, SR-13 diverts from US-43 and becomes a signed route that parallels the U.S. highway to the east. SR-13 leads through rural areas of Fayette, Walker, Winston, Marion and Franklin counties before rejoining US-43.