The Metro Rail Transit Line 7, also known as Mass Rail Transit Line 7, MRT Line 7 or MRT-7, is a rapid transit line under construction in the Philippines. When completed, the line will be 22.8 kilometers (14.2 mi) long, with 14 stations, and the first line to have a third rail electrification. The line runs in a northeast–southwest direction, beginning at San Jose del Monte, Bulacan up to the North Triangle Common Station in North Avenue, Quezon City. It will be the second line to use heavy metro cars after LRT Line 2, which was opened in 2003.

First planned in 2001 and approved in 2004, the 25-year concession agreement was signed in 2008 between the Philippine government and the project's original proponent, Universal LRT Corporation. However, construction has been repeatedly delayed due to right-of-way issues. The project was re-approved in 2013, while funding for the project was obtained in 2016. Construction on the line began the following year and is slated to partially open by 2026 due to route realignment. The project will cost an estimated ₱62.7 billion (US$1.54 billion), with additional plans laid for capacity expansion to accommodate the possible increase in passenger ridership in the future.

It is integrated with the public transit system in Metro Manila, and passengers also take various forms of road-based public transport, such as buses, to and from a station to reach their intended destination.

The 1993 Updated Traffic and Transport Management Plan proposed Line 4, spanning from Welcome Rotonda to Batasan, entirely in Quezon City, for 18.35 km (11.40 mi). A year later, the origins of the proposed route came when the original Line 4 was conceptualized by the presidency of Fidel V. Ramos through a study by SOFRETU, a French firm. Meanwhile, Spanish firms such as Construcciones y Auxiliar de Ferrocarriles, Entrecanales y Tavora, and Cubiertas y MZOV (both later merged to form Acciona) and Halcrow also participated in the study. A year later, Ayala Land and a consortium of French (including Javlon International, Bouygues, and SOFRETU) proposed a line that was to be known as LRT Line 4.

The LRT-4 was supposed to run from Old Bilibid in Manila and traverse along España Boulevard, Quezon Avenue, Elliptical Road, and Commonwealth Avenue before ending at Batasan in Quezon City for the first segment with its length of 15.1 km, while the depot was to be located near the University of the Philippines Diliman. Also, there is a plan to extend to Quirino Highway in Novaliches for 7 kilometers. This was also supposed to have a rolling stock of 5-car light rail vehicles (LRVs) as its rolling stock. The project was approved numerous times in 1995 and first passed in 1998 with a cost of ₱16 billion in budget. It was planned to be done in 1999; however, the plan would be scrapped as the original proposal status was lost in 2003.

As part of the Metro Manila Urban Transportation Integration Study published by the Japan International Cooperation Agency in 1999, which included the Line 4 plan, it called for the construction of a 22.8 km (14.2 mi) elevated railway between Recto Avenue in Manila and Novaliches in Quezon City. A branch line, which would either be an automated guideway transit or busway, would have shuttle commuters to and from San Mateo, Rizal. This proposal would be later split into MRT-7 and the MRT Line 8 proposal. The section of this route between the Quezon Memorial Circle and Novaliches became Line 7 while the rest of the proposed line became Line 8.

On August 27, 2001, an early proposal of the MRT-7 project was submitted to the Department of Transportation and Communications (now the Department of Transportation). When the MRT-7 was proposed, they overlapped the Quezon Memorial Circle to Batasan section, passing along Commonwealth Avenue of the former LRT-4 proposal. The Investment Coordination Committee (ICC) of the National Economic and Development Authority (NEDA) first approved a version of the MRT-7 project in March 2004; this initial approval was provisional and contingent on the project's impact on the government's deficit reduction program. It had been submitted as an unsolicited proposal under the build–operate–transfer scheme by the Universal LRT Corporation, a consortium consisting of Alstom, EEI Corporation, Tyco Electronics, and others. NEDA subsequently authorized the $1.2 billion project's construction the following August, citing the proponents' willingness to comply with the ICC's requirements, with construction slated to begin in 2005 and a targeted opening date in 2007. In October 2004, Universal LRT Corporation signed an agreement with the Manila Banking Corporation to purchase 193 hectares (480 acres) of property in Bulacan for ₱1 billion, stating it would develop this property to complement the rail line.

Universal LRT Corporation, later renamed to what is now SMC-Mass Rail Transit 7 Incorporated, a subsidiary of San Miguel Corporation (SMC) was selected by the Department of Transportation and Communications to build the line in 2008. The concession agreement of the project was signed on June 18, 2008. Construction of the line should have commenced in January 2010, but was postponed several times.