Agathius was a Greek centurion from Cappadocia who served in the imperial army during the early 4th century. Following his arrest in Perinthus for his Christian beliefs, he was subjected to torture by the tribune Firmus. He was eventually taken to Byzantium, where he was scourged and executed by beheading. Because he refused to renounce his faith, he was recognized as a martyr, with his death occurring around the year 303.