Louisa, 2nd Countess of Mansfield (born The Hon. Louisa Cathcart; 1758 – 11 July 1843), was a Scottish noblewoman, who was married twice: first to David Murray, 2nd Earl of Mansfield, and then to The Hon. Robert Fulke Greville. Louisa was the daughter of Charles Cathcart, 9th Lord Cathcart, and his wife, the former Jane Hamilton. She was baptised on 1 July 1758 at Alloa. The countess's portrait was painted by George Romney. She died on 11 July 1843 and was buried in her second husband's family tomb in the chapter house at St Mary's, Warwick.