William III de Ferrers, 5th Earl of Derby (c. 1193 – 28 March 1254) of Chartley Castle in Staffordshire, was an English nobleman and major landowner, unable through illness to take much part in national affairs. From his two marriages, he left numerous children who married into noble and royal families of England, France, Scotland and Wales.
- ^ Cokayne, G. E.; Gibbs, Vicary & Doubleday, H. A., eds. (1926). The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, extant, extinct or dormant (Eardley of Spalding to Goojerat). 5 (2nd ed.). London, p.340, note (d)