Manila Bay (Look ng Maynila; Bahía de Manila) is a natural harbor that serves the Port of Manila (on Luzon), in the Philippines. Strategically located around the capital city of the Philippines, Manila Bay facilitated commerce and trade between the Philippines and its neighboring countries, becoming the gateway for socio-economic development even prior to Spanish occupation. With an area of , and a coastline of , Manila Bay is situated in the western part of Luzon and is bounded by Cavite and Metro Manila on the east, Bulacan and Pampanga on the north, and Bataan on the west and northwest. Manila Bay drains approximately of watershed area, with the Pampanga River contributing about 49% of the freshwater influx. With an average depth of , it is estimated to have a total volume of 28.9 billion cubic meters (28.9 cubic km). Entrance to the bay is wide and expands to a width of . However, width of the bay varies from at its mouth and expanding to at its widest point.
The islands of Corregidor and Caballo divides the entrance into two channels, about towards the North and wide on the South side. Mariveles, in the province of Bataan, is an anchorage just inside the northern entrance and Sangley Point is the former location of Cavite Naval Base. On either side of the bay are volcanic peaks topped with tropical foliage: 40 km to the north is the Bataan Peninsula and to the south is the province of Cavite.
Across the entrance to Manila Bay are several islands, the largest of which is Corregidor, located 3 kilometers from Bataan and, along with the island of Caballo, separates the mouth of the bay into the North and South Channels. In the south channel is El Fraile Island and outside the entrance, and to the south, is Carabao Island. El Fraile, a rocky island some in area, supports the massive concrete and steel ruins of Fort Drum, an island fortress constructed by the United States Army to defend the southern entrance of the bay. To the immediate north and south are additional harbors, upon which both local and international ports are situated.