西门·马吉斯，同时有其他名称如大能者西门、术士西门、行邪术的西门（希腊文：Σίμων ὁ μάγος）是公元1世纪持诺斯底主义的撒马利亚人同时也是西门主义的创始人。他在圣经中有零星记载。一些基督徒认为他是基督教异端，称他为行邪术的西门。

Simon the Sorcerer or Simon the Magician, in Latin Simon Magus (Greek Σίμων ὁ μάγος), was a Samaritan magus or religious figure and a convert to Christianity, baptised by Philip the Evangelist, whose later confrontation with Peter is recorded in Acts 8:9–24. The sin of simony, or paying for position and influence in the church, is named after Simon. The Apostolic Constitutions also accuses him of lawlessness. According to Recognitions, Simon's parents were named Antonius and Rachel.