Au Sable, or Ausable (/ɒˈseɪbəl/ oss-AY-bəl), is a town in Clinton County, New York, United States.

The town is in the southeastern corner of the county, south of Plattsburgh.

Interstate 87, the Adirondack Northway, is an important north–south highway in Au Sable, with access to the town from Exit 34 (Route 9N).

New York State Route 9N runs east–west along the south town line, joining US 9 in Keeseville.

New York State Route 22 is a north–south highway mostly lying west of the Northway.

23.6% of all households were made up of individuals, and 12.1% had someone living alone who was 65 years of age or older.