The Earls of Lancaster were a title in the English nobility, originating in the 13th century. The title was first created for Henry, Earl of Lancaster, a prominent figure during the reign of King Henry III. The earldom played a significant role in the political landscape of medieval England, often associated with the Plantagenet dynasty. The title was held by various members of the Lancaster family, including John of Gaunt, who was a key player in the Hundred Years' War and the father of King Henry IV. The earldom eventually became part of the Duchy of Lancaster, which continues to hold significance in British royal history.