Illustris, was heretofore, in the Roman empire, a title of honour peculiar to people of a certain rank. It was first given to the most distinguished among the knights, who had a right to bear the latus clavus; afterwards, those were intitled illuftrious who held the first rank among those called honorati; that is, the praefecti praetori, praefecti urbis, treasurers, comites, &c.

There were, however, different degrees among the illuftrious: as in Spain they have grandees of the first and second class, so in Rome they had their illuftrious, whom they called great, majoros; and others less, called illuftrios minores.—For instance; the praefectus praetorii was a degree below the master of the offices, though they were both illuftrious.

The Novels of Valentinian distinguish as far as five kinds of illuftrious; among whom, the illuftrious administratores bear the first rank.