Wyandanch (c. 1571 – 1659 was a sachem of the Montaukett Indians in the mid-17th century on eastern Long Island. Initially he was a minor chief among the Montaukett, but due to his skillful manipulation of various alliances and his accommodating stance towards the European colonists who gave him substantial military and economic support, he eventually became an influential "alliance chief" (a sachem who was responsible for maintaining friendly relations between his tribe and the settlers).

The Montaukett ("Metoac"), more commonly known as Montauk are an Algonquian-speaking Native American people from the eastern and central sections of Long Island, New York.