Sir William Plumpton (1404 – 15 October 1480) was a 15th-century English aristocrat, landowner and administrator.
On the death of his father in 1421 he became the ward of Henry Percy, 2nd Earl of Northumberland.
During the War of the Roses he fought on the Lancastrian side at the Battle of Towton in 1461, where his son William and his benefactor Henry Percy, 3rd Earl of Northumberland were slain.
Plumpton was captured but later was pardoned by Edward IV and regained his offices in 1471.
His second wife was Joan Winteringham, whom he later claimed had married in 1451 following the death of Elizabeth; by her he had one son, Robert, who was regarded as heir, as the older Robert had died in 1450 and William had been killed at Towton.