Irnerius, also seen as Hirnerius, Hyrnerius, Iernerius, Gernerius, Guarnerius, Warnerius, Wernerius, Yrnerius, (c. 1050 - after 1125) was an Italian jurist, sometimes referred to as lucerna juris. He taught the free arts at Bologna, his native city.

Of his personal history nothing is known, except that it was at the instance of the countess Matilda, Hildebrand's friend, who died in 1115, that he directed his attention and that of his students to the Institutes and Code of Justinian; that after 1116 he appears to have held some office under the emperor Henry V; and that he died, perhaps during the reign of the emperor Lothair II, but certainly before 1140. He was the first of the Glossators, and according to ancient opinion (which, however, has been much controverted) was the author of the epitome of the Novellae of Justinian, called the Authentica, arranged according to the titles of the Code. His Formularium tabeilionum (a directory for notaries) and Quaestiones (a book of decisions) are no longer extant.

References

• Savigny, Gesch. d. rm. Rechts im Mittelalter, iii. 83
• Vecchio, Notizie di Irnerio e della sua scuola (Pisa, I869)
• Ficker , Forsch. 1. Refi~hs- u. Rechtsgesch. Italiens, vol. iii. (innsbruck, 1870)
• Fitting Die Anfange der Rechtsschule Ia Bologna (Berlin, 1888)