William "Tangier" Smith (February 2, 1655 – February 18, 1705) was a mayor of Tangier, on the coast of Morocco, and an early settler of New York who owned more than 50 miles (80 km) of Atlantic Ocean waterfront property in central Long Island in New York State, in what is called the Manor of St. George. In 1701, he was Acting Governor of New York.
Smith was born in Higham Ferrers, Northamptonshire, in England.
He was sent to join his uncle William Staines in English Tangier and was elected Common Councilman of Tangier in 1677, becoming an alderman there in 1679. He was mayor from 1682 until the English evacuated the colony in October 1683, following attacks by forces under Ismail Ibn Sharif. During Smith's term as mayor, the English destroyed the city's fortifications, as part of the evacuation of the Tangier Garrison.
Smith next settled in the City of London, where he had a trading business in Long Acre.
In 1686, Smith and his wife and three of his children sailed from Cork in Ireland to New York at the urging of Thomas Dongan, 2nd Earl of Limerick, who had been Lieutenant-Governor of Tangier during Smith's years there and had now been named Provincial Governor of New York. Smith's daughter Hibernia died during the passage to North America aboard the ship Thomas.
Smith received grants of land from Lord Limerick and supplemented them with large purchases of Native American land. On May 25, 1691, Smith purchased a substantial tract of the land that is now the Town of Brookhaven, New York, from John Mayhew of the Unkechaug Nation. In exchange, the Unkechaugs were given title to 175 acres (0.71 km2), which has now been reduced to the 55-acre (220,000 m2) Poospatuck Reservation — the smallest reservation in New York state.