Diana Marion Maxwell, Baroness Farnham, DCVO, JP (née Gunnis; 24 May 1931 – 29 December 2021) was a British courtier who served as Lady of the Bedchamber to Queen Elizabeth II from 1987 until her death in 2021.

Born Diana Marion Gunnis on 24 May 1931, she was the elder daughter of Nigel Eric Murray Gunnis, of Branden, Sissinghurst, Kent, and Elizabeth Mary Morrison, a first cousin of Lord Margadale.

In 2012, during the Diamond Jubilee, she notably rode alongside the Queen to St Paul's Cathedral for the Service of Thanksgiving after Prince Philip, Duke of Edinburgh, was hospitalized.

Her funeral was held in the Chapel Royal, St James's Palace, on 14 January 2022.

Mary Morrison represented the Queen, and the Duke and Duchess of Gloucester attended.