The Pasig River (called Ilog Pasig in Filipino) is a river in the Philippines that connects Laguna de Bay to Manila Bay. Stretching for 25 kilometres (15.5 mi), it is lined by Metro Manila on each side. Its major tributaries are the Marikina River and San Juan River.
The Pasig River is technically a tidal estuary, as the flow direction depends upon the water-level difference between Manila Bay and Laguna de Bay. During the dry season, the water level in Laguna de Bay is low and the flow direction of the Pasig River depends on the tides. During the wet season, when the water level of Laguna de Bay is high, flow is normally from Laguna de Bay towards Manila Bay.
The Pasig River used to be an important transport route in Spanish Manila. Due to negligence and industrial development, the river has become very polluted and is considered dead (unable to sustain life) by ecologists.