Earl of Darlington is a title that has been created twice, each time in the Peerage of Great Britain

Peerage of Great Britain

The Peerage of Great Britain comprises all extant peerages created in the Kingdom of Great Britain after the Act of Union 1707 but before the Act of Union 1800...

. The first time was in 1722 for the Baroness von Kielmansegg, half-sister¹ of King George I

George I of Great Britain

George I was King of Great Britain and Ireland from 1 August 1714 until his death, and ruler of the Duchy and Electorate of Brunswick-Lüneburg in the Holy Roman Empire from 1698....

. She was created Baroness Brentford at the same time. This creation was for life only, and so the titles expired on her death in 1730.

The second creation came in 1754 in favour of Henry Vane, 3rd Baron Barnard. For more information on this creation, which became extinct in 1891, see the Baron Barnard

Baron Barnard

Baron Barnard, of Barnard Castle in the Bishopric of Durham, is a title in the Peerage of England. It was created in 1698 for Sir Christopher Vane, who had previously served as a Member of Parliament for County Durham and Boroughbridge. Vane was the son of Sir Henry Vane the Younger and grandson of...

.

Countess of Darlington, First Creation (1722)

• Sophia Charlotte von Kielmansegg, Countess of Leinster and Darlington (1675–1725)

Note

¹ Sophia has often, but erroneously, been asserted to have been mistress of King George I of Great Britain and Ireland: in fact, she was his half-sister. Court ‘observers’ were apparently unable to fathom that George I would have a woman among his intimates without being intimate with her. According to vol. 14 of the Complete Peerage: “The stories that Sophia Charlotte was mistress of George I were demolished in Ragnild Hatton, George I, Elector and King, 1879, pp. 23–4, 134–5.”