The Ausable River , also known as AuSable River and originally written as "Au Sable", runs in the U.S. state of New York, from the Adirondack Mountains and past the village of Lake Placid and Au Sable Forks to empty into Lake Champlain (at 44°33′40″N 73°25′25″W). It has an East and West branch that join at Au Sable Forks. The river forms a partial boundary between Clinton County and Essex County. The Ausable River is known for its gorge, Ausable Chasm, located a few miles east of Keeseville.
The Ausable River is 94 miles (150 km) long and drains a watershed of 516 square miles (1,340 km2).
It was originally named "Au Sable" (French for "sandy") by Samuel de Champlain when he first explored the region in 1609 because of its extensive sandy delta.