Wyandanch (/?wa??n?dænt?/, why-?n-danch) is a hamlet and census-designated place (CDP) in the Town of Babylon in Suffolk County, New York, United States. The population was 11,647 at the 2010 census.
This hamlet is named after Chief Wyandanch, a leader of the Montaukett Native American tribe during the 17th century. Formerly known as Half Way Hollow Hills, West Deer Park (1875), and Wyandance (1893), the area of scrub oak and pine barrens south of the southern slope of Half Hollow terminal moraine was named Wyandanch in 1903 by the Long Island Rail Road (LIRR) to honor Chief Wyandanch and end confusion between travelers getting off at the West Deer Park and Deer Park railroad stations. The history of the hamlet has been shaped by waves of immigrants. No archaeological evidence of permanent Native American settlements in Wyandanch has been discovered. Native Americans hunted and gathered fruits and berries in what is now Wyandanch/Wheatley Heights.