The Pasig River (Filipino: Ilog Pasig; Spanish: Río Pásig) is a water body in the Philippines that connects Laguna de Bay to Manila Bay. Stretching for 25.2 kilometers (15.7 mi), it bisects the Philippine capital of Manila and its surrounding urban area into northern and southern halves. Its major tributaries are the Marikina River and San Juan River. The total drainage basin of the Pasig River, including the basin of Laguna de Bay, covers 4,678 square kilometers (1,806 sq mi).
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 with the river's flow direction dependent on the tides. During the wet season, when the water level of Laguna de Bay is high, the flow is reversed towards Manila Bay.