Date of birth unknown; d. 26 or 27 December, 268. During the pontificate of Pope Stephen (254–57) Dionysius appears as a presbyter of the Roman Church and as such took part in the controversy concerning the validity of heretical baptism (see Baptism under sub-title Rebaptism). This caused Bishop Dionysius of Alexandria to write him a letter on baptism in which he is described as an excellent and learned man (Eusebius [Eusebius of Caesarea (d. c. 339), the first historian of the Church], Hist eccl. VII, vii). Later, in the time of Pope Sixtus II (257–58), the same Bishop of Alexandria addressed Dionysius a letter concerning Lucianus (ibid., VII, ix), who this Lucianus was is not known. After the martyrdom of Sixtus II (6 August, 258) the Roman See remained vacant for nearly a year, as the violence of the persecution made it impossible to elect a new head. It was not until the persecution had begun to subside that Dionysius was raised (22 July, 259) to the office of Bishop of Rome. Some months later the Emperor Gallienus issued his edict of toleration, which brought the persecution to an end and gave a legal existence to the Church (Eusebius, Hist. eccl., VII, xiii). Thus the Roman Church came again into possession of its buildings for worship, its cemeteries, and other properties, and Dionysius was able to bring its administration once more into order. About 260 Bishop Dionysius of Alexandria wrote his letter to Ammonius and Euphranor against Sabellianism in which he expressed himself with inexactness as to the Logos and its relation to God the Father (see Dionysius of Alexandria). Upon this an accusation against him was laid before Pope Dionysius who called a synod at Rome about 260 for the settlement of the matter. The pope issued, in his own name and that of the council, an important doctrinal letter in which, first, the erroneous doctrine of Sabellius was again condemned and, then, the false opinions of those were rejected who, like the Marcionites, in a similar manner separate the Divine monarchy into three entirely distinct hypostases or who represent the Son of God as a created being, while the Holy Scriptures declare Him to have been begotten; passages in the Bible, such as Deut., xxxii, 6, Prov., viii, 22, cannot be cited in support of false doctrines such as these. Along with this doctrinal epistle Pope Dionysius sent a separate letter to the Alexandrian Bishop in which the latter was called on to explain his views. This Dionysius of Alexandria did in his “Apologia” (Athanasius, De sententia Dionysii, V, xiii, De decretis Nicænæ synodi, xxvi). According to the ancient practice of the Roman Church Dionysius also extended his care to the faithful of distant lands. When the Christians of Cappadocia [a region of central Turkey] were in great distress from the marauding incursions of the Goths [Germanic peoples who invaded the Roman Empire, many of them Arian Christians], the pope addressed a consolatory letter to the Church of Caesarea and sent a large sum of money by messengers for the redemption of enslaved Christians (Basilius, Epist. lxx, ed. Garnier). The great synod of Antioch which deposed Paul of Samosata sent a circular letter to Pope Dionysius and Bishop Maximus of Alexandria concerning its proceedings (Eusebius, Hist. eccl., VII, xxx). After death the body of Dionysius was buried in the papal crypt in the catacomb of Callistus.
Liber Pont., ed. Duchesne, I, ccxlviii, 157; Langen, Geschíchte der römischen Kirche (Bonn, 1881), I, 352 sqq.; Hagemann, Die römische Kirche (Freiburg im Br., 1864), 344 sqq., 432 sqq.; Hefele, Konziliengeschichte, 2nd ed., I, 255 sqq.; Bardenhewer, Geschichte der altkirchlichen Literatur (Freiburg im Br., 1903), II, 581 sq.
