The Hoosic River, also known as the Hoosac, the Hoosick (primarily in New York) and the Hoosuck (mostly archaic), is a 76.3-mile-long (122.8 km)[4] tributary of the Hudson River in the northeastern United States.

The different spellings are the result of varying transliterations of the river's original Algonquian name.

The main (South) Branch of the river begins on the west slope of North Mountain and almost immediately fills the man-made Cheshire Reservoir in Berkshire County, Massachusetts.

It then travels through Pownal in the southwest corner of Vermont, after which it enters Rensselaer County, New York.

The river provides the northwest border of the town of Pittstown, then flows through the town of Schaghticoke with its villages of Valley Falls and Schaghticoke before it terminates at its confluence with the Hudson 14 miles (23 km) above the city of Troy.