Which Pope originally conferred the title 'Defender of the Faith' on Henry VIII?

Fidei defensor is a Latin title which translates to Defender of the Faith in English and Défenseur de la Foi in French. The phrase has been used as part of the full style of many monarchs since the early 16th century.

"Defender of the Faith" has been one of the subsidiary titles of the English and later British monarchs since it was granted on 11 October 1521 by Pope Leo X to King Henry VIII of England and Ireland. His wife Catherine of Aragon was also a Defender of the Faith in her own right. The title was conferred in recognition of Henry's book Assertio Septem Sacramentorum (Defense of the Seven Sacraments), which defended the sacramental nature of marriage and the supremacy of the Pope. This was also known as the "Henrician Affirmation" and was seen as an important opposition to the early stages of the Protestant Reformation, especially the ideas of Martin Luther.

Pope Leo X (11 December 1475 – 1 December 1521), born Giovanni di Lorenzo de' Medici, was Pope from 9 March 1513 to his death in 1521. The second son of Lorenzo the Magnificent, ruler of the Florentine Republic, he was elevated to the cardinalate in 1489.