State Route 142 (SR-142) is a two-mile (3 km) long route in Marion County in the northwest part of the state. The western terminus of the route is at a junction with U.S. Highway 278 southwest of Guin. The eastern terminus of the route is at a junction with U.S. Highways 43 and 278 at Guin.

SR-142 begins at an intersection with US-278/SR-118 southwest of Guin, heading northeast on two-lane undivided 11th Avenue. The road passes through forested areas, entering Guin and passing over a BNSF Railway line. The route turns more to the east as it begins to pass homes and businesses. SR-142 continues east into the commercial downtown of Guin, ending at an intersection with US-43/US-278/SR-118/SR-171.

State Route 142 was created in 1982 when U.S. Highway 278 was rerouted along a new roadway south of Guin.

The entire route is in Guin, Marion County.