Pennsylvania Route 978 (PA 978) is a 9.7-mile-long (15.6 km) north–south state highway located in western Allegheny County, Pennsylvania. The southern terminus of the route is at PA 50 in the vicinity of the Cecil area (of Washington County, although the road remains in Allegheny County) and of the Gladden area. The highway heads slightly to the northwest, and reaches the northern terminus at the interchange with U.S. Route 22 (US 22) and US 30 in the Imperial-Enlow area.