Irenaeus of Sirmium was an Illyrian bishop living in Pannonia during the reign of Diocletian. Serving the community in what is now Sremska Mitrovica, he is remembered for his steadfast refusal to perform pagan sacrifices. Despite intense pressure from his own family, including his wife and children, he remained committed to his faith. Following a period of severe torture and imprisonment, he was executed by beheading near the Sava river in 304 AD.