Mary Hill, Marchioness of Downshire and suo jure 1st Baroness Sandys (19 February 1764 – 1 August 1836), was a British peeress. She was born Mary Sandys, daughter of Colonel Martin Sandys (fourth son of Samuel Sandys, 1st Baron Sandys) and his wife Mary Trumbull (only child and heiress of William Trumbull, son of Sir William Trumbull). On 29 June 1786, she married Arthur Hill, Viscount Fairford (who succeeded as 2nd Marquess of Downshire in 1793). They had seven children: