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 Bertrada de Montfort. After doing homage to King Henry III, he had livery of Chartley Castle and other lands of his mother's inheritance. He accompanied King Henry to France in 1230. He sat in parliament in London in the same year. Ferrers married Sibyl Marshal , one of the daughters and co-heirs of William Marshal, 1st Earl of Pembroke. They had seven daughters:

1. Agnes Ferrers (died May 11, 1290), married William de Vesci.
2. Isabel Ferrers (died before November 26, 1260), married (1) Gilbert Basset, of Wycombe, and (2) Reginald de Mohun
3. Maud Ferrers (died March 12, 1298), married (1) Simon de Kyme, and (2) William de Vivonia, and (3) Amaury IX of Rochechouart.
4. Sibyl Ferrers, married (1) John de Vipont, and (2) Franco de Mohun.
5. Joan Ferrers (died 1267), married (1) John de Mohun; (2) Robert Aguillon
6. Agatha Ferrers (died May 1306), married Hugh Mortimer, of Chelmarsh .
7. Eleanor Ferrers (died October 16, 1274), married (1) William de Vaux, and (2) Roger de Quincy, Earl of Winchester, and (3) Roger de Leybourne, but had no issue

In 1238, he married Margaret de Quincy (born 1218), daughter of Roger de Quincy, Earl of Winchester and Helen of Galloway. Bizarrely, Margaret was both the stepmother and stepdaughter of William's daughter, Eleanor. The earl and Margaret had the following children:

1. Robert de Ferrers, 6th Earl of Derby , his successor. He married (1) Mary de Lusignan, daughter of Hugh XI of Lusignan , Count 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, 1st Baron le Despencer, and (2) Eleanor, daughter of Matthew Lovaine.
3. Joan Ferrers (died March 19, 1309) married Thomas Berkeley , Lord Berkeley.
4. Agnes Ferrers married Robert de Muscegros, Lord of Deerhurst.
5. Elizabeth Ferrers, married (1) William Marshal, 2nd Baron Marshal; (2) Prince Dafydd ap Gruffydd

He suffered from gout from youth, and always traveled in a litter. He was accidently thrown from his litter while crossing a bridge, and died of the resulting injuries. William de Ferrers is buried at Merevere Abbey , Warwickshire, England. His widow died on March 12, 1280.

Sources

• Complete Peerage
• Sanders, I.J. English Baronies: A Study of Their Origin and Descent, 1086-1327, 1960
• Weis, Frederick. The Magna Carta Sureties, 1215, 1997