Baron Newcastle is a title in the British peerage, associated with the city of Newcastle upon Tyne. The title was first created in 1643 and has been held by various members of the Cavendish family, particularly during the 18th century. The title is part of the Duke of Newcastle lineage, which has played a significant role in British politics and society. The most notable holder of the title was Thomas Pelham-Holles, the 1st Duke of Newcastle, who served as Prime Minister in the 1750s. The title has been passed down through generations, contributing to the history of the House of Lords and the governance of the United Kingdom.