U.S. Route 15 is a north-south U.S. Highway in Pennsylvania.

US 15 enters Pennsylvania south of Gettysburg, Adams County, from Frederick County, Maryland, on a freeway alignment. The route heads to the north and bypasses Gettysburg, where the route interchanges with US 30. The freeway alignment ends temporarily at York Springs, carrying US 15 on a four-lane, divided alignment until the route upgrades to a freeway again in Dillsburg. The route continues toward Harrisburg, where the freeway terminates again as US 15 joins with US 11. The two routes follow the west shore of the Susquehanna River with limited-access sections until they split across the river from Sunbury. US 15 continues north into Williamsport, joining I-180 and US 220. At I-180's western terminus, US 220, signed south, heads due west toward Jersey Shore and Lock Haven, while US 15 turns due north through Mansfield and crosses into New York near Lawrenceville, Tioga County.

The majority of US 15 is four lanes, alternating between limited and unlimited access. The one leg that is only two lanes is between White Deer and South Williamsport. The segment between Williamsport and the New York state line will eventually be designated Interstate 99.

U.S. Route 15 Business (US 15 Business) is a surface road in Adams County, Pennsylvania that serves as a through street in the Gettysburg area. It marks the original incarnation of US 15, before a freeway bypass was created.

The southernmost portion of the business loop is lightly traveled, serving as a rolling connecting route between the more utilized portions of this highway and a similar business loop in Emmitsburg, Maryland. The road's designation officially begins at the Pennsylvania–Maryland state line in Freedom Township. South of Gettysburg National Military Park, the road is narrow and features infrequent development, while at its southern edges, a small number tourist facilities appear. Traffic picks up greatly during peak travel months through the park, which uses this highway as one of two main access ways. At the northern border of the greenspace, the route becomes Gettysburg's main street, featuring many stoplights and often cars parked on both sides of the street. North of the city center near Gettysburg College, large homes line the street. The highway then turns northeast, passing as an overly narrow route past commercial development, before traveling into sparsely populated farm county. In unincorporated Shrivers Corner, the route meets up with Pennsylvania Route 394, with which it is cosigned for its final one-half mile, as it passes into a US 15 freeway juncture.

U.S. Route 15 Business (US 15 Business) is a surface road in Tioga County, Pennsylvania that serves as a through street in the Mansfield, Pennsylvania area. It marks the original incarnation of US 15, before a freeway bypass was created.

The route begins in the south in an area that features a variety of commercial development, including the area's fast food and big box stores. After passing through a light industrial section, the moves into the borough of Mansfield. The business loop serves as the area's main north-south street, while U.S. Route 6 is the key east-west street. After leaving the borough, it briefly travels along the forested Tioga River, before meeting a freeway junction.