The Marikina River is a river in eastern Metro Manila, Philippines. It is the largest tributary of the Pasig River, with headwaters located in the Sierra Madre Mountains in Rodriguez, Rizal province.

Metropolitan Manila, commonly shortened to Metro Manila and formally the National Capital Region, is the capital region and largest metropolitan area of the Philippines. Located on the eastern shore of Manila Bay, the region lies between the Central Luzon and Calabarzon regions. Encompassing an area of 619.57 km2 (239.22 sq mi) and with a population of 13,484,462 as of 2020, it is composed of sixteen highly urbanized cities: the capital city, Manila, Caloocan, Las Piñas, Makati, Malabon, Mandaluyong, Marikina, Muntinlupa, Navotas, Parañaque, Pasay, Pasig, Quezon City, San Juan, Taguig, and Valenzuela, along with one independent municipality, Pateros. As the second most populous and the most densely populated region in the Philippines, it ranks as the 9th most populous metropolitan area in Asia and the 6th most populous urban area in the world.