Earl of Derby ( ) is a title in the Peerage of England. The title was first adopted by Robert de Ferrers, 1st Earl of Derby under a creation of 1139. It continued with the Ferrers family until the 6th Earl forfeited his property toward the end of the reign of Henry III and died in 1279. Most of the Ferrers property and, by a creation in 1337, the Derby title, were then held by the family of Henry III. The title merged in the Crown upon Henry IV's accession to the throne.