HRH John Charles Francis, Prince of the United Kingdom and Ireland (12 July 1905 - 18 January 1919), son of King George V of the United Kingdom and his wife née Mary of Teck, was a little known member of the royal family: as an epileptic he was kept away from the public eye.

Prince John was born at York Cottage, Sandringham, Norfolk, England, and was baptised 3 August 1905 at St. Mary Magdalen Church, Sandringham, Norfolk.

He had his first epileptic seizure at age four. He was sometimes excluded from official family photographs and did not attend his father's coronation on 22 June, 1911. In 1917 he was sent, with a nanny and male attendants, to Wood Farm on the Sandringham estate, and did not ever see his parents again. He died in his sleep at Wood Farm, Wolferton, Norfolk, England. The King and Queen drove the three miles from their Sandringham estate to view his body: he was buried 21 January 1919 at Sandringham Church, Norfolk.

The name "John" has been considered unlucky and its use avoided by the royal family since the death of the prince. (It was reported that Diana, Princess of Wales wished to name her elder son "John", after her own father, but was prevented from doing so by royal tradition).

The dramatist Stephen Poliakoff produced a mini-series about him called The Lost Prince which aired on BBC One in 2003.