The youngest pope was 11 years old

One of the youngest popes ever was probably John (‘Octavian’) XII (#131), the illegitimate son of Alberic II who ruled Rome from 932 to 954. Alberic, on his deathbed, coerced influential Romans to promise that they would make sure his son, Octavian, would succeed him as the ruler of Rome and also be appointed the next pope. Octavian became John XII [his step-uncle having been John XI (#126)] in December 955 when Agapetus II (#130) died. John was supposed to have been around 18 years of age at that point. The infamous Benedict IX (#146, #148 & 151), who served an unprecedented three terms as pope, was also quite young when first elected in October 1032. He was the last layman to be elected pope. Though there are those that claim that he was but a teenager when elected in reality he was probably in his twenties. THE TEN YOUNGEST POPES SINCE 1400 The youngest pope elected since 1400 was Leo X (#218) at the age of 37, in 1513. He the second son of the famous Lorenzo ‘il Magnifico’ Medici of Florence was created a cardinal, albeit without it being publicized (though this was prior to the in pectore practice that came to be in 1536) when he was but thirteen. Leo X, a cardinal deacon when elected, also happens to be the last non-priest/monk to be elected pope. It is said that on being elected he told his retinue ‘God has given us the papacy. Now let us enjoy it.’ Alak, this was not to be the case. His papacy was majorly buffeted by the rise of Martin Luther’s Reformation. He would die of malaria close to his 46 birthday. The second youngest, since 1400, happens to be Leo X’s cousin Clement VII (#220), one pope later, at the age of 45. [So there is a 8 year difference between the youngest and the second youngest.] Clement VII’s parents were not married making him the last known pope of illegitimate birth.