MRT Line 3 (Metro Manila)

The Manila Metro Rail Transit Line 3, also known as the MRT Line 3 or MRT-3, is a rapid transit line in Metro Manila in the Philippines. The line runs in an orbital north to south route following the alignment of Epifanio de los Santos Avenue (EDSA). Despite its name, the line is more akin to a light rapid transit system owing to its tram-like rolling stock while having total grade separation and high passenger throughput. Originally known as the Metrostar Express or the Blue Line, the line was reclassified to be the Yellow Line in 2012.

Envisioned in the 1970s and 1980s as part of various feasibility studies, the 13-station, 16.9-kilometer (10.5 mi) line was the second rapid transit line to be built in Metro Manila when it started full operations in 2000. The line is owned and operated by the Philippine government's Department of Transportation (DOTr). It was previously owned by the Metro Rail Transit Corporation (MRTC) under a 25-year build–lease–transfer agreement with the DOTr, which expired on July 15, 2025.

The line is integrated with the public transit system in Metro Manila, where passengers also take various forms of road-based public transport, such as buses, to and from a station to reach their intended destination. Serving close to 400,000 passengers on a daily basis, the line is the busiest among Metro Manila's three rapid transit lines. Total ridership significantly exceeds its built maximum capacity of 350,000 passengers a day, with various solutions being proposed or implemented to alleviate chronic congestion. Expanding the network's capacity to accommodate the rising number of passengers is currently set on tackling this problem.