Valentinianism is a Gnostic movement founded by Valentinus in the second century CE.

Valentinianism is one of the major Gnostic movements.

Its influence is extremely widespread, not just within Rome, but also from Egypt through Asia Minor and Syria in the east, and Northwest Africa.Later in the movement’s history it breaks into two schools, an Eastern school and a Western school.

Disciples of Valentinus continue to be active into the 4th century CE, after the Roman Empire is declared to be Christian.Valentinus and the Gnostic movement that bear his name are considered threats to Christianity by church leaders and Christian scholars, not only because of their influence, but also because of their doctrine, practices and beliefs.

Gnostics are condemned as heretics, and prominent Church fathers such as Irenaeus of Lyons and Hippolytus of Rome write against Gnosticism.

Most evidence for the Valentinian theory comes from its critics and detractors, most notably Irenaeus, since he was especially concerned with refuting Valentinianism.