Pennsylvania Route 478 (PA 478) is a 2.20-mile-long (3.54 km) state highway located in Clarion and Venango counties.

The highway serves the eastbound interchange for Exit 45 on Interstate 80 (I-80) and terminates at PA 58 in St. Petersburg.

After I-80, PA 478 turns from its southward progression to the southeast, crossing through dense forestry.

The highway soon turns back to the south, paralleling Freeman Road and entering the borough of St. Petersburg.

[3] However, the next year, the alignment was designated as part of PA 238, which ran from Saint Petersburg to Shippensville.