He was probably born near the city of Idanha-a-Velha (in Lusitania, Hispania), in what is present-day Portugal, or near the city of Castelo Branco (also in Lusitania, now Central Portugal), then part of the Western Roman Empire. His life coincided with the rise of Constantine I and the reunion and redivision of the Western and Eastern Roman Empire as well as what is sometimes known as the Constantinian shift associated with the widespread legitimization of Christianity and the later adoption of Christianity as the religion of the Roman state.
Damasus I is known to have been raised in the service of the church of the martyr St. Laurence (Basilica of Saint Lawrence outside the Walls) in Rome, and following the death of Pope Liberius, he succeeded to the Papacy amidst factional violence. A group of Damasus' supporters, previously loyal to the Antipope Felix II, attacked and killed rivals loyal to Liberius' deacon Ursinus, in a riot that required the intervention of Emperor Valentinian I to quell.
Damasus faced accusations of murder and adultery in his early years as pope. The neutrality of these claims have come into question with some suggesting that the accusations were motivated by the schismatic conflict with the supporters of Arianism. His personal problems were contrasted with his religious accomplishments, which included restoring the basilica, appointing St. Jerome as his personal secretary, creating (through Jerome) a standard Latin translation of the Bible, known as the Vulgate--replacing the existing Vetus Latina, and translated from the original Hebrew instead of the Greek Septuagint--and presiding over the Council of Rome in 382, at which, according to Roman Catholic tradition and the 6th century document Decretum Gelasianum, the modern Catholic canon of scripture was first set down.
Damasus' parents were Antonius, a priest at the Church of San Lorenzo in Rome, and Laurentia. During Damasus' early years, Constantine I rose to rule first the Western Roman Empire, presiding over the Edict of Milan (313) and winning religious freedom for Christians in all parts of the Roman Empire. A crisis precipitated by the rejection of religious freedom by Licinius, Emperor of the Eastern Roman Empire, in favor of paganism resulted in a civil war (324) that placed Constantine firmly in control of a reunited Empire, and led to the establishment of Christian religious supremacy in Constantinople, called Nova Roma as well as Rome, bringing new challenges to the authority of the Roman Church. Damasus would have been in his twenties at the time.
On the death of Liberius, September 24, 366, one faction supported Ursinus who had served as deacon to Liberius, while the other faction, previously loyal to the Antipope Felix II, supported Damasus. The upper-class partisans of Felix supported the election of Damasus, but the opposing supporters of Liberius, the deacons and laity, supported Ursinus; the two were elected simultaneously (Damasus' election was held in San Lorenzo in Lucina), in an atmosphere of rioting. Supporters already clashed at the beginning of October. Such was the violence and bloodshed that the two prefects (praefecti) of the city were called in to restore order, and after a first setback, when they were driven to the suburbs and a massacre of 137 was perpetrated in the basilica of Sicininus (as cited in Ammianus Marcellinus), the prefects banished Ursinus to Gaul. There was further violence when he returned, which continued after Ursinus was exiled again.
Church historians, such as St. Jerome and Rufinus, championed Damasus. At a synod in 378 Ursinus was condemned and Damasus exonerated and declared the true pope. The former antipope continued to intrigue against Damasus for the next few years, and unsuccessfully attempted to revive his claim on Damasus's death. Ursicinus was among the Arian party in Milan, according to Ambrose (Epistle iv).
This dissension climaxed with a riot which led to a three-day massacre and to the rare intervention of Emperor Valentinian I to uphold public order. Damasus prevailed, but only with the support of the city prefect. Once he was securely consecrated bishop of Rome, his men attacked Ursinus and his remaining supporters who were seeking refuge in the Liberian basilica, resulting in a massacre of one hundred and thirty seven supporters of Ursinus. Damasus was also accused of murder before a later prefect, but his rich friends secured the personal intervention of the emperor to rescue him from this humiliation. The reputations of both Damasus and the Roman church in general suffered greatly due to these two unseemly incidents.
Damasus I was active in defending the Roman Church against the threat of schisms. In two Roman synods (368 and 369) he condemned Apollinarianism and Macedonianism, and sent legates to the First Council of Constantinople that was convoked in 381 to address these heresies.
Damasus appointed Church historian Jerome, whom he appointed his confidential secretary. In Jerome's letter of 409 (letter cxx.10 ), he remarks, "A great many years ago when I was helping Damasus, bishop of Rome with his ecclesiastical correspondence, and writing his answers to the questions referred to him by the councils of the east and west [if "east and west" do not betray the passage as an interpolation] Jerome spent three years (382-385) in Rome in close intercourse with Pope Damasus and the leading Christians. Invited there originally to a synod of 382 convened to end the schism of Antioch, he made himself indispensable to the pope, and took a prominent place in his councils.
Damasus encouraged the highly respected scholar to revise the available Old Latin versions of the Bible into a more accurate Latin on the basis of the Greek New Testament and the Septuagint, in order to put an end to the marked divergences in the western texts of that period, resulting in the Vulgate. Jerome devotes a very brief notice to Damasus in De viris illustribus, written after Damasus' death: "he had a fine talent for making verses and published many brief works in heroic metre. He died in the reign of the emperor Theodosius at the age of almost eighty" (ch. 103).
St. Damasus sat in the Chair of St. Peter eighteen years and two months. His feast day is December 11.
These ceremonial embellishments and the emphasis on the Roman legacy of Peter and Paul amounted to a general claim to the Roman upper classes that the real glory of Rome was Christian and not pagan. All this made it more socially acceptable for the upper classes to convert to Christianity. Often, the women of the family were the first to abandon pagan ways, while the men tended to hold on to them longer, being generally more conservative in their idealised views on the greatness of the Empire.
The reign of Gratian, during Damasus' papacy, forms an important epoch in ecclesiastical history, since during that period (359-383), Orthodox Christianity, for the first time became dominant throughout the empire. Under the influence of Ambrosius, Gratian prohibited pagan worship at Rome; refused to wear the insignia of the pontifex maximus as unbefitting a Christian; removed the Altar of Victory from the Senate at Rome, despite protests of the pagan members of the Senate, and confiscated its revenues; forbade legacies of real property to the Vestals; and abolished other privileges belonging to them and to the pontiffs.
During his papacy Peter II was obliged for a while to seek refuge to Rome from the persecuting Arians , he was received by Pope Damasus I; who sympathised with him and gave him support against the Arians. and this reconciled the relations between the Church of Rome and the church of Antioch , who supported the Church of Alexandria
Damasus' devotion for the Roman martyr is attested also by the tradition, according to which the pope built a church devoted to Laurence in his own house, San Lorenzo in Damaso.
Some scholars disagree that this was a genuine letter from Jerome.