| Earldom of Castleton | |
| Creation Date: | 18 June 1720 |
| Last Holder: | James Saunderson, 1st Earl |
| Remainder To: | Heirs male of the first earl's body lawfully begotton |
| Subsidiary Titles: | Viscount Castleton (GB, 1716) Viscount Castleton (Ire, 1627) Baron Saunderson (GB, 1714) Baron Saunderson (Ire, 1627) Baronet (of Saxby) |
| Status: | Extinct |
| Extinction Date: | 23 May 1723 |
| Motto: | Je suis veillant à plaire ("I am watchful to please") or Sans Dieu rien ("Without God, nothing")[1] |
The title Earl Castleton, of Sandbeck in the County of York, was created in the Peerage of Great Britain in 1720 for the 6th Viscount Castleton, who had previously been created Baron Saunderson, of Saxby in the County of Lincoln, in 1714, and Viscount Castleton, of Sandbeck in the County of York, in 1716, both also in the Peerage of Great Britain.[2]
The title Viscount Castleton, in the County of Limerick, had been created in the Peerage of Ireland in 1627, along with the subsidiary title Baron Saunderson, of Bantry in the County of Cork, for Sir Nicholas Saunderson, 1st Baronet, who had been created a Baronet, styled "of Saxby in the County of Lincoln", in the Baronetage of England, in 1611.[3]
All of the titles became extinct on the death of the 1st Earl in 1723. His estates passed to his cousin Lieutenant-Colonel Thomas Lumley, who thereupon took the additional surname of Saunderson by Act of Parliament and subsequently succeeded as 3rd Earl of Scarbrough.[4]