Manila Bay is a natural harbor that serves the Port of Manila, 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 1,994 km², and a coastline of 190 km, 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 17,000 km² of watershed area, with the Pampanga River contributing about 49% of the freshwater influx. With an average depth of 17 m, it is estimated to have a total volume of 28.9 billion cubic meters. Entrance to the bay is 19 km wide and expands to a width of 48 km. However, width of the bay varies from 22 km at its mouth and expanding to 60 km at its widest point.
The islands of Corregidor and Caballo divides the entrance into two channels, about 2 mi towards the North and 6.5 mi wide on the South side.