Wassaic is a hamlet and census-designated place in the town of Amenia, Dutchess County, New York, United States. As of the 2020 census, its population is 210. Located in southeastern New York in the valley of the Ten Mile River, Wassaic is bordered to the east and west by mountain ranges. The name of the hamlet is derived from the Native American word Washaic; "land of difficult access" or "narrow valley".