Henrietta Ponsonby, Countess of Bessborough, born Lady Henrietta Frances Spencer, was the wife of Frederick Ponsonby, 3rd Earl of Bessborough; the couple were the parents of Lady Caroline Lamb. Her father, John Spencer, 1st Earl Spencer, was a great-grandson of John Churchill, 1st Duke of Marlborough. Her sister was Georgiana Cavendish, Duchess of Devonshire.

Frederick Ponsonby, 3rd Earl of Bessborough, styled the Viscount Duncannon from 1758 to 1793, was an Anglo-Irish peer.