Pope John I (Latin: Ioannes I; died 18 May 526) was the bishop of Rome from 13 August 523 to his death. He was a native of Siena (or the "Castello di Serena", near Chiusdino), in Italy. He was sent on a diplomatic mission to Constantinople by the Ostrogoth King Theoderic to negotiate better treatment for Arians. Although John was relatively successful, upon his return to Ravenna, Theoderic had him imprisoned for allegedly conspiring with Constantinople. The frail pope died of neglect and ill-treatment.