Simon Magus (Greek Σίμων ὁ μάγος), also known as Simon the Sorcerer and Simon of Gitta, was a Samaritan proto-Gnostic and traditional founder of the Simonians in the first century A.D. His only Biblical reference is in Acts 8:9-24 and prominently in several apocryphal and heresiological accounts of early Christian writers, some of whom regarded him as the source of all heresies, particularly St. Justin who wrote about Simon about one hundred years after his life.