Byzantine philosopher, skilled dialectician, and imputed heretic who, at the imperial court, established a school of Platonism that advanced the work of integrating Christian with pagan Greek thought. Italus exerted a lasting influence on the Byzantine mind.

Of Calabrian origin, Italus, after a period of court favour under the emperor Michael VII Ducas (1071–78), was suspected of treason while on a diplomatic mission to Italy but was later exonerated. With the exile of his tutor, Michael Psellus, he succeeded to the title first philosopher of Constantinople. In a synod of 1082 he was charged with rationalizing the Christian mysteries, particularly the ineffable manner of the God–man union in Christ, and with reviving the doctrines of the pre-existence and transmigration of souls, as enunciated by pre-Christian philosophers. Confined to a monastery, he publicly retracted any neo-pagan implications in his teaching and was consequently pardoned.

Italus' distinction derives from his attempt, in 93 short tracts, to synthesize Platonic metaphysics with Aristotelian logic. His eclecticism greatly influenced the later theories of 14th- and 15th-century Italian humanism.