Wyandanch is a hamlet and census-designated place in the Town of Babylon in Suffolk County, New York, United States. The population was 12,990 at the time of 2020 census. In the past, some or all of Wyandanch was proposed to become part of the never-realized Incorporated Village of Half Hollow Hills and later on proposed incorporating itself as the Incorporated Village of Wyandanch. However, those plans failed and Wyandanch has never been incorporated.