The Norristown High Speed Line is a 13.4-mile (21.6 km) interurban light rapid transit line operated by SEPTA, running between the 69th Street Transportation Center in Upper Darby and the Norristown Transportation Center in Norristown, Pennsylvania. Originally the Philadelphia and Western Railroad line, the line runs entirely on its own right-of-way. By 2020, the Norristown High Speed Line had an average weekday ridership approaching 11,000 passengers.

The interurban is a type of electric railway, with tram-like electric self-propelled rail cars which run within and between cities or towns. The term "interurban" is usually used in North America, with other terms used outside it. They were very prevalent in many parts of the world before the Second World War and were used primarily for passenger travel between cities and their surrounding suburban and rural communities. Interurban as a term encompassed the companies, their infrastructure, their cars that ran on the rails, and their service. In the United States, the early 1900s interurban was a valuable economic institution, when most roads between towns, many town streets were unpaved, and transportation and haulage was by horse-drawn carriages and carts.