Dubbed as the country's "Project of the Century", the Metro Manila Subway broke ground on February 27, 2019,[8] and construction began the following December.

Passengers may take various forms of road-based public transport, such as buses and jeepneys, to and from a station to reach their intended destination.

[10] The idea of building a subway in the Greater Manila Area had been forwarded as early as 1973, when the JICA (at the time known as the Overseas Technical Cooperation Agency or OTCA) and former Secretary of Public Works and Highways David Consunji conducted a study on what shall later be Metro Manila (formally constituted on November 7, 1975).

[22] It was also proposed to be part of the 1977 Metro Manila Transport, Land Use and Development Planning Project (MMETROPLAN), which was funded by the World Bank.

[16] In 1995, the Mexican firm Grupo ICA, which also experienced Mexico City Metro, was in talks with the Department of Public Works and Highways (DPWH) to build a subway in the Philippines.

[25] In 1998, the Department of Transportation and Communications (DOTC, later DOTr) signed a memorandum of understanding (MOU) with JK International Ltd. to conduct a feasibility study of a subway project; a route would have been linked between Port of Manila and NAIA.

The project was proposed once more in the 2014 Metro Manila Dream Plan as a 57.7-kilometer (35.9 mi) line that would serve as the second north–south mass transit backbone for the newly expanded Greater Capital Region (the first being the North–South Commuter Railway).

The Metro Manila Dream Plan (formally titled the Roadmap for Transport Infrastructure Development for Metro Manila and Its Surrounding Areas) is an integrated plan, created on the basis of recommendations from a study conducted by the Japan International Cooperation Agency (JICA).

Locate optimal sites for subway stations and determine their basic requirements at least for the first 150 km; hire top-level consultants to prepare detailed engineering designs for the initial 150 km of tubes and various stations, optimal performance standards, environmental impact, economic and social benefits, value for money, and geotechnical and other technical analyses.

[18] In 2015, the National Economic and Development Authority approved the construction of the Makati-Pasay-Taguig Mass Transit System Loop Line 5 (MTSL Line 5), which would have been a 20-kilometer-long (12 mi) underground railway from BGC to Taft Avenue, as identified in the JICA study, with two options: 32nd Street or 26th Street.

In September 2020, the Department of Transportation (DOTr) presented one of the six tunnel boring machines in an acceptance test ceremony through a video conference.

[9] On July 10, 2023, the DOTr scrapped its plan to begin partial operations by 2027, opting instead to fully open the subway by 2029.

The project involves the construction of 17 stations in its first phase (listed from north to south):[76] The following phases of the subway project would involve extending lines up to San Jose del Monte, Bulacan, north of Metro Manila (15.4 kilometers or 9.6 miles from General Luis Avenue in Caloocan), and down to Dasmariñas, Cavite, south of Metro Manila (20.7 kilometers or 12.9 miles from the proposed Ninoy Aquino International Airport station).

[77] The initial plan was later modified in June 2020, with DOTr adding the East Valenzuela, Lawton, and Senate stations.

Assessment of the environmental and geographical considerations in the base alignment (initially 74.6 kilometers or 46.4 miles long) recommends 18% of the line to be at-grade and 9% to be running through viaduct.

[77] Prior to final approval, some adjustments to the alignment were done so that it would reduce the risk of damage during earthquakes by travelling along solid adobe ground.

On September 5, 2020, in response to questions, Transportation Secretary Arthur Tugade provided assurances that the system would be flood-proof.

[82] The stations would have design features such as water-stop panels, a high-level entrance for flood prevention, earthquake detection, and a train stop system, akin to the Tokyo subway.

[4] The Metro Manila Subway will use Sustina electric multiple units built by the Sumitomo Corporation and Japan Transport Engineering Company (J-TREC).

[2] Hitachi, along with Sumitomo and Mitsubishi, bought bid documents for the design, execution, and completion of 30 train sets in February 2020.

[61] In addition, a 900-meter (3,000 ft) test track and mock-ups of the tunnels, stations, and wayside equipment will be constructed for training purposes.

[87] In the 2023 plan, when the government approves the 194 flagship infrastructure projects, the subway's extension will lead to Bulacan and Cavite.

Also included in the plan is a 4-kilometer (2.5 mi) extension to Asia World, which will connect to the Paranaque Integrated Terminal Exchange (PITX) and its namesake LRT-1 station.

[88] The planned extensions are under study and are expected to be financed by the Asian Development Bank (ADB) under the Infrastructure Preparation and Innovation Facility.

At the time, transportation secretary Jaime Bautista said that the subways would be expanded to Cavite, and he also said there would be three to four lines.

[90] In the following year, JICA also said there will be future subways, and this time, they also conducted a study for a 30-year railway master plan for the Greater Capital Region.