Maryland Route 342 (MD 342) is a state highway in the U.S. state of Maryland. Known as St. Augustine Road, the state highway runs 2.82 miles (4.54 km) from MD 310 in St. Augustine north to unsigned MD 537 in Chesapeake City in southern Cecil County. MD 342 was constructed in its entirety by 1915.

MD 342 begins at an intersection with MD 310 (Cayots Corner Road) in St. Augustine. The state highway heads northeast as a narrow two-lane road through farmland. MD 342 makes a right-angle turn to the northwest, curves to the west, then takes a sharp turn to the north through a forested area and scattered residences. Just east of the southern end of the Chesapeake City Bridge, the state highway enters the town of Chesapeake City and intersects an unnamed road (unsigned MD 537D) that leads to ramps to MD 213 (Augustine Herman Highway). MD 342 continues a short distance to its northern terminus at an oblique junction with George Street, which is unsigned MD 537C and leads to MD 286 in the South Chesapeake City Historic District.

MD 342 was paved from George Street to just south of the right-angle turn by 1910. The remainder of the road to St. Augustine and MD 310 east of St. Augustine were built as a state-aid road by 1915. MD 342 has changed very little since then.

The entire route is in Cecil County.