Photinus of Sirmium (fl. 340–376 CE) was born in Galatia. He served as deacon to Marcellus of Ancyra when he was bishop (Bishop [Episcopos]) of Ancyra and reportedly endorsed and elaborated upon his theological ideas (Jer. Vir. ill. 107; Socr. Hist. eccl. 2.18). It is unclear when Photinus became bishop of Sirmium. Records do not mention him among the bishops at the Council of Sardica (343 CE), which restored Marcellus and Athanasius of Alexandria to their sees; however, one chronicler suggests that Photinus was bishop by then…