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date: 18 July 2019

Constantine I the Great

The Oxford Dictionary of Late Antiquity
David GwynnDavid Gwynn, Oliver NicholsonOliver Nicholson

Constantine I the Great (emperor 306–37) 

The first Christian Roman emperor and one of the decisive figures of Western history.

Early life, rise to power, and supreme rule

Constantine was born in 272/3 at Naissus (Niš) in the Balkans. His father Constantius I rose to become a Caesar in Diocletian’s Tetrarchy, although Constantine’s mother Helena was apparently of humbler birth. Constantius became Augustus on the abdication of Diocletian and Maximian on 1 May 305, but died at York on 25 July 306. Constantine was with his father when he died and was promptly hailed as emperor by Constantius’ army.

Constantine’s authority during the six years of civil war and internal tension which followed was initially restricted to Gaul, Britain, and Spain. However, on 28 October 312, having marched through northern Italy, Constantine defeated his western rival Maxentius outside Rome at the Battle of the Milvian Bridge and took possession also of Italy and Africa. The following February Constantine’s sister was married to Licinius, the emperor at that time in charge of the Balkans. The alliance freed Licinius to attack and defeat his eastern rival Maximinus Daza, so that by the end of that summer Constantine in the West and Licinius in the East were the only emperors left.

The alliance with Licinius was not secure. In 316 Constantine attacked his colleague, marching across the Balkans and winning a battle at Cibalae. However, the Cibalensean War was not decisive, and on 1 March 317 the two emperors made peace; they proclaimed as their Caesars Constantine’s adult son Crispus and Licinius’ baby boy, also called Licinius, and Constantine took possession of all Licinius’ European territories except Thrace.

The peace did not last. In 321 the two emperors refused to recognize each other’s nominees for the consulship and in 324 Constantine attacked again. This time he led an army across Thrace while his son Crispus commanded a fleet which defeated Licinius’ admiral at the Dardanelles, so making decisive Constantine’s victory at the Battle of Chrysopolis on the Asian side of the Sea of Marmara on 18 September. Constantine received Licinius' surrender the following day at Nicomedia of Bithynia. The following 8 November he founded Constantinople and proclaimed as a Caesar his son Constantius II (then aged 7).

Constantine had four sons, but in 326 his eldest son Crispus by his first wife Minervina was executed for obscure reasons. Constantine’s second wife Fausta was killed at around the same time. On Constantine’s death in 337 the empire was divided among his three sons by Fausta: Constantine II, Constantius II, and Constans.

Relations with Christians

When Constantine became an emperor in 306, the Great Persecution had been in progress for over three years. Lactantius clearly states that Constantine’s first act upon becoming an emperor was to suspend the Great Persecution in the territories which he controlled (Mort. 24, 9). Evidence about any earlier associations Constantine may have had with Christianity is tenuous and circumstantial. It may be that his mother Helena had Christian connections before the Great Persecution, but definite evidence of her Christian piety all dates from after 324. Constantine chose the Christian apologist Lactantius as tutor to the ill-fated Crispus, so it may be that Constantine and Lactantius had been acquainted at Nicomedia before the persecutions when Constantine was a young officer at Diocletian’s court. The author of a panegyric reports that in 310 Constantine had a religious vision of the Sun (PanLat. VII (VI), 21), but the significance of this is unclear. In 312, during the Milvian Bridge campaign, occurred the famous Vision of the Cross; although neither of the two contemporary Christian sources who report this event calls it a conversion, it was clearly a religious experience, and no doubt the victory over Maxentius in the ensuing battle confirmed Constantine’s sense that he and the Christian God were fighting on the same side.

Certainly from this point onwards it is possible to see Constantine’s involvement in Christian affairs. In the summer of 313, after Licinius had defeated Maximinus Daza, Licinius issued instructions to provincial governors in the East, the Letter of Licinius, effectively bringing to an end the persecution of the Christians; the terms had been agreed between Licinius and Constantine earlier in the year (Lactantius, Mort. 48, 2–12; Eusebius, HE X, 5, 2–14).

At the same time Constantine funded the foundation of the cathedral of Rome, the Constantinian Basilica, now S. John Lateran (Liber Pontificalis, 39). Christian property lost during the Great Persecution was restored (Letter to Anullinus, in Eusebius, HE X, 5), the imperial treasury was opened to bishops (Letter to Caecilian, in Eusebius, HE X, 6), and Constantine legalized the Church’s right to receive bequests (CTh XVI, 2, 4 of 321). Bishops gained additional legal privileges over the manumission of slaves and enlarged powers of mediation in bishops’ courts (episcopalis audientia), while clergy received exemption from curial duties (Letter to Anullinus, in Eusebius, HE X, 7).

Constantine also tried to resolve the Donatist Controversy in Africa, a conflict arising from disagreement about the conduct of bishops during the Great Persecution. In 314 he took the step, unprecedented for an emperor, of summoning a council and making the Cursus Publicus available to the bishops who travelled to Arles to attend it. Constantine compared the council’s judgement to that of God (Letter to the Bishops, in Optatan Appendix, 5), but was unable to enforce the verdict against the Donatists. Resolution was not achieved for another century.

Later, when he came to the East in 324, Constantine discovered deeper divisions afflicting the eastern Church, where the doctrinal debates now known as the ‘Arian Controversy’ were already raging. Initially, Constantine expressed the hope that the ‘trivial’ and ‘unworthy’ questions in dispute could be settled amicably (Letter to Alexander and Arius, in Eusebius, VCon 2, 64–72). Once he recognized the significance of the debates, Constantine summoned what became the first œcumenical council to Nicaea in May–July 325. The largest Christian gathering yet held, the Council of Nicaea also witnessed his Vicennalia (20th anniversary) celebrations, which Eusebius compared to ‘an imaginary representation of the kingdom of Christ’. After the final session he invited the bishops to dine at the palace (VCon III, 15). The composition of the original Nicene Creed unfortunately failed to resolve all the questions at issue. Over the following decade Constantine exiled several leading bishops, including Eusebius of Nicomedia and Athanasius of Alexandria, but his quest for harmony was again in vain and the questions involved did not reach a lasting resolution till the Council of Constantinople in 381.

In the following year his mother Helena visited the Holy Land where she founded churches at Bethlehem, where Jesus was born, and on the Mount of Olives, where he gave his last teaching and ascended into heaven. Around the same time Constantine ordered the destruction of the principal pagan temple at Jerusalem. The demolition crew discovered the Tomb of Christ, the scene of the Resurrection, and Constantine promptly ordered that a church should be built over the place; the building work was seen by the Bordeaux Pilgrim in 333 and the church was ready for consecration in 336.

It was probably during the Easter vigil at Nicomedia in 325 that Constantine delivered to the Christians at his *court the lengthy address known as the Oration to the Holy Assembly (Oratio ad Sanctos). The speech starts by celebrating the resurrection of Christ and places it in a philosophical context. It goes on to place the Christian mission into a broader historical context, in a way which would have seemed familiar to any reader of Lactantius’ Divine Institutes—and incidentally is the first Christian utterance to interpret Vergil’s Fourth Eclogue as a prophecy of the birth of Christ. It ends with an extensive exposition of the notion that the Christian God punishes persecuting emperors—precisely the argument of Lactantius' On the Deaths of the Persecutors. The whole is suffused with the conviction not only that Constantine has the support of the Christian God, but that he is actually doing God’s work. The same conviction is advanced in surviving letters written by the emperor and preserved in full by Eusebius’ Life of Constantine, notably a general letter to the provincials of Palestine (Letter to the Provincials of Palestnie, in VCon II, 24, 42) and diplomatic letters to the King of Persia, the youthful Shapur II, to whose care he commends the Christians of the Persian Empire (Personal Letter to the King of Persia in VCon IV, 8–13). It is true that Constantine did not himself receive baptism until he was in his last illness, but this was not at all unusual for potential Christians who held public positions of responsibility and did not wish to be subject to the regime of penance as it was administered in the 4th century. Constantine’s sense of mission is palpable: ‘The Supreme…examined my service and approved it as fit for his own purposes’ (VCon II, 28, 2).

Constantine and traditional religion

What is remarkable about Constantine’s policy towards Christians is the complete reversal of fortune which it represents. A religion which the previous regime had tried to repress suddenly received unprecedented favour. It is the first step which counts.

It did not, of course, mean that all practice which might be deemed pagan disappeared immediately. At some point Constantine made a law against sacrifice. The law itself is lost but it is cited in a law of 341 made by his son Constans I (CTh XVI, 10, 2). Temple treasures were confiscated including bronze from their roofs (Eusebius, VCon III, 54) Some temples were destroyed, including that at Jerusalem and others at Aphaca (the birthplace of Adonis), of Aesculapius at Aegae of Cilicia and at Heliopolis (Baalbek), still a stronghold of paganism in the 6th century (Eusebius, VCon III, 55–8). Others were not: ‘let them keep if they wish their sanctuaries of falsehood’ (Letter to the Eastern Provincials, in VCon II, 56, 2).

Mars and Hercules appear occasionally on Constantine’s coins as late as 320/1, as does the Sun, but Christians were quite capable of appropriating the Sun as symbolic of their Most High God. When Constantine declared Sunday to be a day of rest in 321 he hailed the Dies Solis, the day of the sun (CTh II, 8, 1) and permitted Christian soldiers to attend church while commanding non-Christian soldiers to attend a religious parade where a monotheistic prayer was recited (Eusebius, VCon IV, 18–20).

His non-Christian subjects reacted in various ways. The pagan poet Palladas was not afraid to express his disgust. The Roman Senate was more circumspect. The Arch of Constantine, which they erected in 315 next to the Colosseum, attributed Constantine’s success to ‘the inspiration of the divinity (instinctu divinitatis)’, a careful phrase acceptable to Christians and pagans alike. Even the imperial cult survived in a modified form. One of Constantine’s sons approved a petition from Hispellum in Umbria for a temple and priesthood honouring the imperial family, although he insisted that the temple ‘must not be defiled by the evils of any contagious superstition’ (CIL IX, 5265). Constantine did not mince words when expressing his disgust at the pollution caused by pagan practice but if Eusebius truly thought the emperor encouraged the building of churches because soon ‘almost everybody would in future belong to God, once the polytheistic madness had been removed’, Eusebius was an optimist (VCon II, 45).

Secular matters

The impact of Constantine went far beyond religion. He replaced the Tetrarchic system from which he had emerged, and reunited the Roman world under a single ruler, while recognizing that it was necessary to have cooperation between those responsible for defence of the three principal frontiers, on the Rhine, on the Danube, and in the East. He was in fact fortunate that following on the cracking victory of Galerius of 298 all was quiet on the eastern front until the final year of his reign. He campaigned, however, against the Sarmatians on the Danube frontier.

The political and economic reforms initiated under the Tetrarchy were completed, fulfilling the transition from the Third Century Crisis to the more stable conditions of the 4th century. Constantine introduced the solidus as the dominant gold unit of the late Roman economy.

Above all, Constantine is associated with Constantinople. Work began at the site of the ancient city of Byzantium shortly after Constantine’s conquest of the east, and the new city was consecrated on 11 May 330. The urban layout resembled other Tetrarchic cities like Trier and Nicomedia, but Constantinople swiftly surpassed those rivals and acquired the title ‘New Rome’. Its geographic location as an administrative and economic centre and its defensive strength made Constantinople the greatest city of the Eastern Roman and Byzantine Empire.

In his last years, Constantine came into conflict with Sasanian Persia. Constantine was preparing for war in 337 when his final illness struck. According to Eusebius, the emperor desired to be baptized in the River Jordan but was unable to complete the journey and so received baptism in Nicomedia. Constantine died at Pentecost, on 22 May 337, and was buried in his mausoleum church of the Holy Apostles in Constantinople (VCon IV, 61–73).

David Gwynn; Oliver Nicholson


More of Constantine’s personal utterances survive than is known from almost any other Roman emperor. His Easter sermon the Oration to the Holy Assembly is preserved among the works of Eusebius, and is in need of re-editing:

ed I. A. Heikel, Eusebius Werke, I (GCS 7, 1902), 151–92.Find this resource:

ET M. J. Edwards in his Constantine and Christendom (TTH 39, 2004), 1–62.Find this resource:

Many of Constantine’s letters survive, preserved by Eusebius of Caesarea (HE X and VCon) and in the Optatan Appendix, 3, 5–7, 9–10.

For the years up to 313, Lactantius, On the Deaths of the Persecutors, written in 313/15, provides essential detail. The dedications of the second edition of his Divine Institutes reflect his estimate of the emperor, and his other works give insight into the Christianity of Constantine’s circle.

Eusebius’s Church History (HE) provides the impressions of a provincial bishop, frequently revised by the author, up to 325.

Eusebius’ Life of Constantine is a panegyrical biography by a man who had met Constantine and corresponded with him but was not an intimate. It was long regarded with suspicion particularly by H. Grégoire and others, as Constantine is, after all, the subject of considerable later fiction. However, the publication in 1954 of a papyrus of one of the imperial letters preserved in the Life has caused opinions to be revised.

ed. F. Winkelmann, Eusebius. Über das Leben des Kaiser Konstantins: Eusebius Werke, I, 1 (GCS 57, rev. edn. 1991).Find this resource:

ET (with introd. and comm.) Averil Cameron and S. G. Hall, Eusebius: Life of Constantine (1999).Find this resource:

A. H. M. Jones and T. C. Skeat, ‘Notes on the Genuineness of the Constantinian Documents in Eusebius’s Life of Constantine’, JEH 5 (1954), 196–200.Find this resource:

Eusebius’ Panegyric of Constantine and Speech on the Holy Sepulchre:

ed. I. A. Heikel, Eusebius Werke, I (GCS 7, 1902), 193–259.Find this resource:

ET (annotated) H. A. Drake, In Praise of Constantine: A Historical Study and New Translation of Eusebius Tricennial Orations (University of California Publications, Classical Studies 15, 1976).Find this resource:

T. Grünewald, Constantinus Maximus Augustus. Herrschaftspropaganda in der zeitgenössischen Überlieferung (Historia Einzelschrift 64, 1990) collects references to other sources, particularly inscriptions.Find this resource:

RIC VII covers Constantine’s coinage.

PLRE I, Constantinus 4.

NEDC analyses the sources (39–43) and catalogues Constantine’s movements (68–80).


The bibliography on Constantine is enormous and space is available only for more recent work.

T. D. Barnes, Constantine and Eusebius (1981) marked a watershed in the empirical study of Constantine, as it was based on a close reading of the sources. References to Barnes’s subsequent work, and a useful summary of earlier historiography, may be found in:Find this resource:

T. D. Barnes, Constantine: Dynasty, Religion and Power in the Later Roman Empire (2011).Find this resource:

P. Stephenson, Constantine: Unconquered Emperor, Christian Victor (2009) is a recent biography.Find this resource:

Among works concerned with specific aspects may be noted the following:

John Noel Dillon, The Justice of Constantine: Law, Communication, and Control (2012) is concerned with law and administration.Find this resource:

H. A. Drake, Constantine and the Bishops: The Politics of Intolerance (2000) considers Constantine and the Church.Find this resource:

N. Lenski, ed., The Cambridge Companion to the Age of Constantine (rev. edn. 2012) collects essays on a range of topics.Find this resource:

R. Van Dam, The Roman Revolution of Constantine (2007) uses two inscriptions to consider the impact of Constantine on those he ruled.Find this resource:

J. Bardill, Constantine, Divine Emperor of the Christian Golden Age (2011) is good on the physical evidence for Constantine.Find this resource:

E. Hartley, J. Hawkes, M. Henig, with F. Mee, eds., Constantine the Great: York’s Roman Emperor (2006) is an exhibition catalogue with helpful essays.Find this resource: