State Route 55 (SR 55) is a primary state highway in the U.S. state of Virginia. Known for most of its length as John Marshall Highway, the state highway runs from the West Virginia state line, where the highway continues as West Virginia Route 55 (WV 55), east to U.S. Route 29 (US 29) in Gainesville. West of its interchange with Interstate 81 (I-81) in Strasburg, SR 55 runs concurrently with the easternmost portion of US 48 as part of Corridor H. East of Front Royal, the state highway serves as the local complement of I-66 as it passes through the towns of Marshall, The Plains, and Haymarket.