A Christian Gnostic teacher active in Alexandria in the early second century. Born in the Egyptian Delta, he was educated in Alexandria. He is reported by to have the teachings of the Gnostic sect in creating his own system, which conformed to a greater degree to traditional doctrine. Around 140 he moved to Rome, where he became active in ecclesiastical affairs. has a brief summary of a Gnostic myth taught by Valentinus.

He was also a composer of epistles, homilies, and poetry, of which only small fragments are preserved in writings of Clement of Alexandria and of Rome. Some scholars also attribute to him the (NHC I, 3; XII, 2), extant in a Coptic translation of the original Greek. Valentinus had a number of prominent pupils who became active in Alexandria, Rome, and elsewhere, and his school spread into all areas of the Roman Empire and beyond, into Mesopotamia. Christianity persisted in some areas into the seventh century.