scholar and teacher, who founded a school of Gnosticism known as the Basilidians. He probably was a pupil of Menander in Antioch, and he was teaching in Alexandria at the time of the Roman emperors Hadrian and Antonius Pius.

Clement of Alexandria, a Christian theologian of the 3rd century AD, wrote that Basilides claimed to have received a secret tradition—on which he apparently based his gnosis, or esoteric knowledge—from Glaucias, an interpreter of the Apostle Peter. In addition to psalms and odes, Basilides wrote commentaries on the Gospels and also compiled a “gospel” for his own sect; only fragments of these writings have been preserved. Contradictory accounts of Basilides' theology have been provided by Clement, as well as by the theologians Hippolytus of Rome and Saint Irenaeus. While interpreters cite elements of Neoplatonism, the New Testament, and other Gnostic systems, description of the Basilidian system of belief remains incomplete.

Basilides was succeeded by his son, Isidore, and the Basilidian school still existed in Egypt in the 4th century. Its followers were the first to keep the day of Jesus' baptism on January 6 or 10, celebrating it with an all-night vigil.