Sarah Fane, Countess of Westmorland (née Sarah Anne Child; 28 August 1764 – 9 November 1793) was the only child of Robert Child, the owner of Osterley Park and principal shareholder in the banking firm Child & Co. She married John Fane, 10th Earl of Westmorland on 20 May 1782 at Gretna Green after they eloped together. Her parents were dissatisfied with the match: Sarah Anne being an only child, her father wanted her to marry a commoner who would take the Child name; but Sarah Anne told her mother, "A bird in the hand is worth two in the bush." Her father cut her out of his will, leaving his house and fortune to Sarah Anne's second son or eldest daughter, instead of the Westmorland heir.
Sarah Anne and the earl's surviving children were:
As only one son survived, most of Child's fortune eventually went to his eldest granddaughter, Lady Sarah Sophia.