JOHN I., pope from 523 to 526, was a Tuscan by birth, and was consecrated pope on the death of Hormisdas. In 525 he was sent by Theodoric at the head of an embassy to Constantinople to obtain from the emperor Justin toleration for the Arians; but he succeeded so imperfectly in his mission that Theodoric on his return, suspecting that he had acted only half-heartedly, threw him into prison, where he shortly afterwards died, Felix IV. succeeding him. He was enrolled among the martyrs, his day being May 27.