(Fidei Defensor, ) A peculiar title belonging to the king of England; as Catholicus to the king of Spain, and Christianissimus to the king of France. These titles were given by the popes of Rome. That of Fidei Defensor was first conferred by Leo X. on king Henry VIII. for writing against Martin Luther; and the bull for it bears date quinto idus, October 1521. It was afterwards confirmed by Clement VII. But the pope, on Henry's suppressing the houses of religion, at the time of the reformation, not only deprived him of his title, but deposed him from his crown also; though, in the 35th year of his reign, his title, &c. was confirmed by parliament, and has continued to be used by all his successors. Chamberlayne says, the title belonged to the kings of England before that time, and for proof thereof appeals to several charters granted to the University of Oxford: so that pope Leo's bull was only a renovation of an ancient right.