The Pittsburgh Light Rail is a 26.2-mile (42.2 km) light rail system in Pittsburgh, Pennsylvania, and surrounding suburbs. It operates as a deep-level subway in Downtown Pittsburgh, but runs mostly at-grade in the suburbs south of the city. The system is largely linear in a north-south direction, with one terminus near Pittsburgh's central business district and two termini in the South Hills. The system is owned and operated by Pittsburgh Regional Transit. The T is one of the surviving first-generation streetcar systems in North America, with the oldest portions of the network dating back to 1903 and the Pittsburgh Railways. It is also one of only three light rail systems in the United States that continues to use the broad 5 ft 2+1⁄2 in Pennsylvania Trolley Gauge on its lines instead of the 4 ft 8+1⁄2 in standard gauge. In 2023, the system had a ridership of 3,417,100.

Light rail transit (LRT) is a form of passenger urban rail transit characterized by a combination of tram and rapid transit features. While its rolling stock is similar to that of a traditional tram, it operates at a higher capacity and speed and often on an exclusive right-of-way. In many cities, light rail transit systems more closely resemble, and are therefore indistinguishable from, traditional underground or at-grade subways and heavy-rail metros.