Johannes de Deo

Rubric from the start of the Liber poenitentiarius in an Austrian manuscript of . The elongated initial belongs to Incipit liber ('the book begins') and the name Johanne de Deo is in the third line from the top. Johannes de Deo ( – 15 March 1267) was a Portuguese priest, judge and scholar of canon law who taught for over twenty years at the University of Bologna. He was a prolific writer.

Life Johannes was called Hispanus, meaning a native of the Iberian Peninsula. He was born in Silves during the brief period when it was held by King Sancho I of Portugal between 1189 and 1191. He refers to himself as a priest, and seems to have been ordained in Lisbon before studying at the University of Bologna. He studied canon law and possibly civil law at Bologna from 1223 until 1229. He was a professor at Bologna from 1229 until at least 1255. He appears to have been a doctor of both laws. The titles he uses of himself are doctor decretorum (doctor of decrees) and utriusque juris professor (professor of both laws). Liber quaestionum (6 September 1248), dedicated to Cardinal Ottaviano Ubaldino His Liber poenitentiarius became the new standard for penitentials.

Few of Johannes' works have been printed. An exception is Principium decretalium, which has been edited by Hermann Kantorowicz.