Markus von Arethusa was a 4th-century bishop and martyr from Arethusa, Syria. He participated in the Council of Serdica in 343 and the Council of Sirmium in 352, where he helped draft a confession intended to resolve the theological dispute regarding the nature of Christ. Although he was once accused of Arianism, he was later rehabilitated. During the reign of Emperor Julian, he faced persecution for destroying a pagan temple, leading to his eventual martyrdom.