Mar Shimun Bar Sabbae (Classical Syriac: ܡܪܝ ܫܡܥܘܢ ܒܪܨܒܥܐ, died Good Friday, 345) was Bishop of Seleucia-Ctesiphon, from Persia, the de facto head of the Church of the East, until his death. He was bishop during the persecutions of King Shapur II of the Sasanian Empire of Iran, and was executed along with many of his followers. He is revered as a saint in various Christian communions.