d.526. Pope from 523. He was Tuscan. His pontificate was marked by much friction with Theodoric the Ostrogothic ruler at Rome who adopted a very severe policy against the orthodox Catholics in Italy as his answer to an equally stringent policy by Justin against the Arians of the Eastern Empire. John went to Constantinople to secure a reversal of this policy, and he was partially successful. But on his return to Italy he was imprisoned by Theodoric and died in Ravenna.