Son of John, a physician, a Marsian from the province and town of Valeria; he succeeded Boniface III after a vacancy of over nine months; consecrated 25 August, 608; d. 8 May, 615 (Duchesne); or, 15 September, 608-25 May, 615 (Jaffé).
In the time of Pope St. Gregory the Great he was a deacon of the Roman Church and held the position of dispensator, i.e., the first official in connexion with the administration of the patrimonies. Boniface obtained leave from the Emperor Phocas to convert the Pantheon into a Christian Church, and on 13 May, 609 (?) the temple erected by Agrippa to Jupiter the Avenger, to Venus, and to Mars was consecrated by the pope to the Virgin Mary and all the Martyrs. (Hence the title S. Maria Rotunda.) It was the first instance at Rome of the transformation of a pagan temple into a place of Christian worship. Twenty-eight cartloads of sacred bones were said to have been removed from the Catacombs and placed in a porphyry basin beneath the high altar.
During the pontificate of Boniface, Mellitus, the first Bishop of London, went to Rome "to consult the pope on important matters relative to the newly established English Church" (Bede, H. E., II, iv). Whilst in Rome he assisted at a council then being held concerning certain questions on "the life and monastic peace of monks", and, on his departure, took with him to England the decree of the council together with letters from the pope to Lawrence, Archbishop of Canterbury, and to all the clergy, to King Ethelbert, and to all the English people "concerning what was to be observed by the Church of England". The decrees of the council now extant are spurious. The letter to Ethelbert (in William of Malmesbury, De Gest. Pont., I, 1464, ed Migne) is considered spurious by Hefele (Conciliengeschichte, III, 66), questionable by Haddan and Stubbs (Councils, III, 65), and genuine by Jaffé [Regest. RR. PP., 1988 (1548)].
Between 612-615, St. Columban, then living at Bobbio in Italy, was persuaded by Agilulf, King of the Lombards, to address a letter on the condemnation of the "Three Chapters" to Boniface IV, which is remarkable at once for its expressions of exaggerated deference and its tone of excessive sharpness. In it he tells the pope that he is charged with heresy (for accepting the Fifth Council, i.e. Constantinople, 553), and exhorts him to summon a council and prove his orthodoxy. But the letter of the impetuous Celt, who failed to grasp the import of the theological problem involved in the "Three Chapters", seems not to have disturbed in the least his relation with the Holy See, and it would be wrong to suppose that Columban regarded himself as independent of the pope's authority.
During the pontificate of Boniface there was much distress in Rome owing to famine, pestilence, and inundations. He died in monastic retirement (he had converted his own house into a monastery) and was buried in the portico of St. Peter's. His remains were three times removed: in the tenth or eleventh century, at the close of the thirteenth under Boniface VIII, and to the new St. Peter's on 21 October, 1603. For the earlier inscription on his tomb see Duchesne; for the later, Groisar, "Analecta Romana", I, 193.