December 4th 1154: Nicholas Breakspear became Pope Adrian IV (r. 1154-59), the only Englishman ever to become pontiff.
December 5th 1590: Election of Gregory XIV (r. 1590-91), the third pope to reign in a single year.
December 8th 1854: Pope Pius IX (r. 1846-78) issued Ineffabilis Deus, which defined the dogma of the Immaculate Conception of the Virgin Mary.
December 9th 1565: Death of Pope Pius IV (r. 1559-65). 1669: Death of Pope Clement IX (r. 1667-69).
December 10th 1936: Death of Luigi Pirandello (b. 1867), author of the famous play Sei Personaggi in Cerca d’Autore (Six Characters in Search of an Author).
December 11th 1610: Death of the German painter Adam Elsheimer (b. 1578).
December 14th 867: Election of Adrian II (r. 867-72), the last married pope. Pope Adrian II died exactly five years later.
December 17th 1213: Death of St John of Matha, founder of the Order of the Most Holy Trinity, better known as the Trinitarians. 1538: Excommunication of King Henry VIII by Pope Paul III (r. 1534-49).
December 20th 69 CE: Death of the Roman Emperor Vitellius, who reigned for only eight months. 1720: Birth of Charles Edward Stuart (d. 1788), also known as Bonnie Prince Charlie or 'the Young Pretender', who is interred in St Peter's Basilica.
December 21st 1737: Death of the Florentine architect and mathematician Alessandro Galilei (b. 1691). 1863: Death of the poet Giuseppe Gioachino Belli (b. 1791).
December 23rd 1655: Triumphal entry of Christina of Sweden, who was queen until her abdication in 1654, following her conversion to Catholicism.
December 24th 1294: Election of Cardinal Benedetto Caetani as Pope Boniface VIII (r. 1294-1303).
December 25th 800: Pope Leo III (r. 795-816) crowned Charlemagne as Holy Roman Emperor in St Peter’s Basilica.
December 26th 1559: Election of Pope Pius V (r. 1559-65).
December 30th 39 CE: Birth of the emperor Titus Flavius Vespasianus (r. 79-81). 1591: Death of Pope Innocent IX, who only reigned for 62 days. 2012: Death of the scientist Rita Levi-Montalcini (b. 1909), who was awarded the Nobel Prize for Medicine in 1986. December 31st 192: Assassination of the emperor Commodus (r. 177-192). 335: Death of Pope Sylvester I (r. 314-35). In Italy, New Year's Eve is known as the Festa di San Silvestro, in honour of Pope Sylvester I. 1619: Death of the architect Onorio Longhi (b. 1568). 2022: Death, at the age of 95, of Pope Emeritus Benedict XVI.