The Pasig River is a river in the Philippines and connects Laguna de Bay via the Napindan Channel into Manila Bay. The river is called Ilog Pasig in Filipino language Filipino. It stretches for 25 kilometers and divides Metro Manila into two. Its major tributaries are the Marikina River and San Juan River Philippines San Juan River.

The Pasig River is technically a tidal estuary in that 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. However, due to negligence and industrial development, the river has become very Pollution polluted and is considered dead unable to sustain life by ecologists.

The Pasig River Rehabilitation Commission (PRRC) was estalished to oversee rehabilitation efforts for the river. Supporting the PRRC are private sector organizations i.e. Clean and Green Foundation, Inc. who implemented the Piso para sa Pasig Filipino: A peso for the Pasig campaign.