William de Ferrers, 5th Earl of Derby (1193 - March, 1254), was an English nobleman.

He was born in Derbyshire, England, the son of William de Ferrers, 4th Earl of Derby and Agnes of Chester, a daughter of Hugh of Kevelioc, Earl of Chester and Bertrade de Montfort. After doing homage to King Henry III, he had livery of Chartley Castle and other lands of his mother's inheritance. He sat in parliament in London in the same year. Ferrers married Sybil Marshal, one of the daughters and co-heirs of William Marshal, Earl of Pembroke. They had seven daughters:

1. Agnes Ferrers, married William de Vesci. 2. Isabel Ferrers, married (1) Gilbert Basset, of Wycombe, and (2) Reginald de Mohun. 3. Maud Ferrers, married (1) William de Kymes, and (2) William de Vyvon, and (3) Emerick de Rupel Carnardi. 4. Sibil Ferrers, married (1) John de Vipont, and (2) Franco de Mohun. 5. Joane Ferrers, married William Aguillon, and (2) John de Mohun. 6. Agatha Ferrers, married Hugh Mortimer, of Chelmarsh. 7. Eleanor Ferrers, married (1) William de Vallibus, and (2) Roger de Quincy, Earl of Winton, and (3) Roger de Leybourne, but had not issue

In 1238, he married Margaret de Quincy (born 1218), daughter of Roger de Quincy, Earl of Winchester and Helen of Galloway. The earl and Margaret had the following children: 1. Robert de Ferrers, 6th Earl of Derby, his successor. He married (1) Mary le Brun, daughter of Hugh le Brun, Earl of Angoulême, and niece of King Henry III, by whom he had no issue; and (2) Eleanor Basset, daughter of Ralph Basset, Lord Basset, by whom he had an only son, John 2. William Ferrers obtained, by gift of Margaret, his mother, the manor of Groby in Leicestershire, assuming the arms of the family of De Quincy. He married (1) Anne le Despencer, daughter of Hugh le Despencer, and (2) Eleanor, daughter of Matthew Lovaine. 3. Joan Ferrers married Thomas Berkeley, Lord Berkeley. 4. Agnes Ferrers married Robert de Musegros, Lord of Deerhurst.

William de Ferrers is buried at Merevere Abbey, Warwickshire, England. His widow died on March 12, 1280.

Preceded by: William de Ferrers

Earl of Derby

Followed by: Robert de Ferrers