Prince John

Prince John refers most commonly to the following:

*King John of England (1166-1216), who was known as "Prince John" during the reigns of his father and older brother
*"Prince John", a primary villain in the Robin Hood stories, who is an exaggerated and fictionalized version of the above. See also Prince John (Disney)
*Prince John of the United Kingdom (1905-1919), the youngest son of King George V, a fragile boy who suffered from epilepsy and near-autism

Other members of the British royalty known as "Prince John" include:
*John of Eltham, Earl of Cornwall (1316-1336), second son of Edward II
*John of Gaunt, 1st Duke of Lancaster (1340-1399), third son of Edward III
*John of Lancaster, 1st Duke of Bedford (1389-1435), second son of Henry IV
*Prince Alexander John of Wales (1871), third son and youngest child of Edward VII who died shortly after birth

Other uses:
*The "Prince John" was a former Grand Trunk Pacific Railway passenger steamship that was transferred to the Canadian National Railway