Agnes Duff, Countess Fife

Lady Agnes Georgiana Elizabeth Hay (12 May 1829 – 18 December 1869) was an Irish-Scottish aristocrat.

Agnes was born at Dublin, Ireland. She was the third child of William Hay, 18th Earl of Erroll and Elizabeth FitzClarence, one of the illegitimate children of William IV and his mistress Dorothea Jordan.

Agnes died at the age of 40. Her only son, Alexander, married Princess Louise of Wales, the eldest daughter of Albert Edward, Prince of Wales (later Edward VII) and Alexandra of Denmark (later Queen Alexandra) in 1889 and was created Duke of Fife by Queen Victoria. Through her fourth daughter, also named Agnes, she is an ancestor of British prime minister David Cameron.

She married James Duff, 5th Earl Fife, son of General Hon. Sir Alexander Duff and Anne Stein, on 16 March 1846 at British Embassy, Paris, France.

They had six children