Pennsylvania Route 158 (PA 158) is an 11.9-mile-long (19.2 km) state highway located in western Pennsylvania, running from PA 18 south of New Wilmington in Lawrence County, to US 62 and PA 258 in Mercer in Mercer County.

Traveling north from PA 18, PA 158 heads through a rural area of northern Lawrence County that is home to an Amish community and into the borough of New Wilmington, where it passes Westminster College and intersects with PA 208.

As it leaves the borough, it enters Mercer County and winds northeasterly through rural countryside nearly 6 miles (9.7 km) before it passes over I-80.

Approximately 3 miles (4.8 km) later, the route enters the borough of Mercer, where it meets the eastern terminus of PA 318 just one block before its own northern terminus at the US 62/PA 258 concurrency.

[5] The bridge was completely reconstructed in 2020, and the route was deleted as a result.