Wassaic is a hamlet and census-designated place in the town of Amenia, Dutchess County, New York, United States. 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". However, Europeans found ready access by following the Housatonic River valley up from Long Island Sound and through the mountains along the Ten Mile River.