V. (Ottobuono de' Fieschi), pope in 1276, was a Genoese who was created cardinal deacon by his uncle Innocent IV. In 1264 he was sent to England to mediate between Henry III. and his barons. He was elected pope to succeed Innocent V. on the 11th of July 1276, but died at Viterbo on the 18th of August, without having been ordained even to the priesthood.