Honorius of Thebes, a possibly mythical character from the Middle Ages, is said to have authored The Sworn Book of Honorius, although the first printed manuscript of this work did not appear until 1629. Considerable mystery still exists about the identity of Honorius, both Pope Honorius I and Pope Honorius III have been linked to the character. Honorius of Thebes is also claimed to be the creator of the Theban alphabet, in Heinrich Cornelius Agrippa's De Occulta Philosophia (1531) and Johannes Trithemius's Polygraphia (1518).
According to the Sworn Book of Honorius, he is supposed to be "the son of Euclid, master of the Thebians". But the book delivers no source to whom this might be.