Illiterate popes

Several popes are regarded by historians as illiterate, including:
 * Pope Zephyrinus (199–217) — The Refutation of All Heresies includes the observation that "Pope Zephyrinus was illiterate."
 * Pope Adrian IV (1154–1159) — George Washington Dean writes: "Adrian IV., the only English Pope, had been an illiterate servant in a monastery at Avignon."
 * Pope Celestine V (1294) — The Lanercost Chronicle records: "On the commemoration day of S. Paul [June 30], Celestinus the Fifth was created Pope, who, albeit illiterate, was the priest and confessor of his predecessor."

Wrongly regarded as illiterate
Ludwig von Pastor has shown that Pope Julius II (1503–1513) was not illiterate, although he is poetically referred to as such by Desiderius Erasmus.