Sir Lionel Duckett (1511 – August 1587) was one of the merchant adventurers of the City of London.
He was four times Master of the Mercers' Company, and Lord Mayor of London in 1572.
He was born in 1511 to William Duckett of Flintham, Nottinghamshire and his wife Jane (née Redman), of Harwood Castle, Yorkshire.
He subscribed to Martin Frobisher's three voyages in search of the Northwest Passage, and to John Hawkins' voyage of 1562 which led to the formation of the Africa Company, paving the way for the Atlantic slave trade in later centuries.
His nephew Stephen (c.1548–1591, son of his brother John) succeeded him as lord of the manor of Calne.