He came to Rome during the pontificate of Gregory III and gradually rose to high office in the service of successive popes.
After the deposition of Antipopes Constantine II and Philip, Stephen was chosen to succeed him. Fragmentary records are preserved of the council (April 769) at which the degradation of Constantine was completed, certain new arrangements for papal elections made, and the practice of devotion to icons confirmed (see iconoclasm). The politics of Stephen's reign are obscure, but he inclined to alliance between the Papacy and the Lombards rather than to the Franks. He was succeeded by Adrian I.
