Agnes Leslie, Countess of Morton was a Scottish noblewoman, being the daughter of George Leslie, 4th Earl of Rothes as well as a great-granddaughter of King James II. She was the wife of William Douglas, 6th Earl of Morton, who as Laird of Lochleven Castle was the custodian of Mary, Queen of Scots during her captivity from June 1567 until her escape on 2 May 1568. Agnes was Queen Mary's chief female companion throughout her imprisonment; thus it was while Lady Agnes was recovering from childbirth that the queen successfully escaped from Lochleven.

William Douglas, 6th Earl of Morton was the son of Robert Douglas of Lochleven and Margaret Erskine, a former mistress of James V of Scotland.