The foundation of Constantinople in 330 AD marks the conventional start of the Byzantine Empire, which fell to the Ottoman Empire in 1453 AD. Only the emperors who were recognized as legitimate rulers and exercised sovereign authority are included, to the exclusion of junior co-emperors who never attained the status of sole or senior ruler, as well as of the various usurpers or rebels who claimed the imperial title.
The following list starts with Constantine the Great, the first Christian emperor, who rebuilt the city of Byzantium as the imperial capital, Constantinople, and who was regarded by the later emperors as the model ruler. Modern historians distinguish this later phase of the Roman Empire as the Byzantine Empire due to the imperial seat moving from Rome to Byzantium, the Empire's integration of Christianity, and the predominance of Greek over Latin.
The Byzantine Empire was the direct legal continuation of the eastern half of the Roman Empire following its division in 395. Emperors listed below up to Theodosius I in 395 were sole or joint rulers of the entire Roman Empire. The Western Roman Empire continued until 476. Byzantine emperors considered themselves Roman emperors in direct succession from Augustus; the term "Byzantine" became conventional in Western historiography in the 19th century. The use of the title "Roman Emperor" by those ruling from Constantinople was not contested until after the papal coronation of the Frankish Charlemagne as Holy Roman emperor (25 December 800).
The title of all emperors preceding Heraclius was officially "Augustus", although other titles such as Dominus were also used. Their names were preceded by Imperator Caesar and followed by Augustus. Following Heraclius, the title commonly became the Greek Basileus (Gr. Βασιλεύς), which had formerly meant sovereign, though Augustus continued to be used in a reduced capacity. Following the establishment of the rival Holy Roman Empire in Western Europe, the title "Autokrator" (Gr. Αὐτοκράτωρ) was increasingly used. In later centuries, the emperor could be referred to by Western Christians as the "emperor of the Greeks". Towards the end of the Empire, the standard imperial formula of the Byzantine ruler was "[Emperor's name] in Christ, Emperor and Autocrat of the Romans" (cf. Ῥωμαῖοι and Rûm).
Dynasties were a common tradition and structure for rulers and government systems in the Medieval period. The principle or formal requirement for hereditary succession was not a part of the Empire's governance; hereditary succession was a custom and tradition, carried on as habit and benefited from some sense of legitimacy, but not as a "rule" or inviolable requirement for office at the time.
Throughout the history of the Byzantine Empire, the vast majority of emperors originated from the state's traditional military recruitment grounds. During the early imperial period, many rulers hailed from the Latin-speaking regions of the Balkans (Illyricum) and Thrace, whereas in subsequent centuries the leadership was predominantly drawn from Anatolia and Thrace. Individuals of Armenian origin or descent also represented a notable and recurring element within the imperial succession, producing several prominent rulers and dynasties. Empress Irene of Athens represents the sole documented instance in Byzantine history of a ruler born in the Greek peninsula.
Constantinian dynasty (306–363)
+ Portrait Name Reign Notes Constantine I"the Great" 25 July 306 – 22 May 337 Born at Naissus 272 as the son of the Augustus Constantius and Helena. Proclaimed Augustus of the western empire upon the death of his father on 25 July 306, he became sole ruler of the western empire after the Battle of the Milvian Bridge in 312. In 324, he defeated the eastern Augustus Licinius and re-united the empire under his rule, reigning as sole emperor until his death. Constantine completed the administrative and military reforms begun under Diocletian, who had begun ushering in the Dominate period. Actively interested in Christianity, he played a crucial role in its development and the Christianization of the Roman world by convening the First Ecumenical Council at Nicaea. He is said to have received baptism on his deathbed. He also reformed coinage by introducing the gold solidus, and initiated a large-scale building program, culminating in the refounding of the city of Byzantium as "New Rome", popularly known as Constantinople. He was regarded as the model of all subsequent Byzantine emperors. His reign was marked by greater imperial control over the Eastern Church and the construction of new churches, especially at the holy places sacred to Christianity. To this day, Constantine is venerated as a saint by the Eastern Orthodox church. Constantius II 9 September 337 – 3 November 361 Born on 7 August 317, as the second surviving son of Constantine I, he inherited the eastern third of the Roman Empire upon his father's death, sole Roman Emperor from 353, after the overthrow of the western usurper Magnentius; after two years on the run, the latter committed suicide. Constantius' reign saw military activity on all frontiers, and dissension between Arianism, favored by the emperor, and the supporters of the Nicene Creed. In his reign, Constantinople was accorded equal status to Rome, and the original Hagia Sophia was built. Constantius appointed Constantius Gallus and Julian as Caesares, and died on his way to confront Julian, who had risen up against him. Julian "the Apostate" 3 November 361 – 26 June 363 Born in May 332 at Constantinople (the first emperor born there), Julian was the grandson of Constantius I and cousin of Constantius II. Proclaimed by his army in Gaul, he became the legitimate Emperor upon the death of Constantius II. Julian has been described as the last pagan emperor of the Roman Empire and was generally opposed to Christianity. He was killed on campaign against Sassanid Persia, despite his initial success in surrounding the ancient city of Ctesiphon. For his adherence to the old Roman gods and rejection of the Christian faith, he became known as Julian the Apostate. Jovian 27 June 363 – 17 February 364 Born in , Jovian hailed from a military family and was captain of the guards (protector domesticus) under both Constantius II and Julian. He was elected by the army upon Julian's death. After assuming power, Jovian withdrew Roman forces from Persia and made an unpopular peace with them, which lasted until the early sixth century. Following an autumn spent in Antioch, he died of natural causes in central Anatolia and was buried in Constantinople.
Valentinian dynasty (364–392)
+ Portrait Name Reign Notes Valentinian I "the Great" 25/26 February 364 – 17 November 375 Born in 321. An officer under Julian and Jovian, he was elected by the army upon Jovian's death. He soon appointed his younger brother Valens as Emperor of the East, while he himself ruled in the West. Died of cerebral haemorrhage in 375. Valens 28 March 364 – 9 August 378 Born in 328, Valens was not especially fit for the imperial office if Ammianus can be believed, but he was appointed Emperor of the East in 364 by his elder brother Valentinian I, who wanted a malleable colleague in the other half of the Empire. Following Valentinian's death in 375, his son Gratian succeeded him. Meanwhile, Valens faced the challenge of the invading Huns, whose ferocity pushed the Gothic tribes to seek refuge within the Empire; Valens allowed them to settle on the condition that they become allies of the Empire. When the Goths were mistreated at Roman hands and rebelled, Valens proceeded to face them without awaiting assistance from Gratian's armies and was killed at the Battle of Adrianople. Gratian 9 August 378 – 19 January 379 Born 18 April 359, Gratian was emperor of the Western Roman Empire from 367 until his death in 383. The eldest son of Valentinian I, Gratian, was raised to the rank of Augustus as a child and inherited the West after his father's death in 375. Gratian led a campaign across the Rhine, attacked the Lentienses, and forced the tribe to surrender. That same year, the eastern emperor Valens was killed fighting the Goths at the Battle of Adrianople. Gratian then elevated Theodosius to replace him in 379. Gratian phrases out the title of Pontifex maximus, replacing it with the Latin phrase: Pontifex inclytus ("honorable pontiff"). Procopius () 28 September 365 – 27 May 366 Maternal cousin of Julian; revolted against Valens and captured Constantinople, where the people proclaimed him emperor. Deposed, captured, and executed by Valens.
Theodosian dynasty (379–457)
+ Portrait Name Reign Notes Theodosius I"the Great" 19 January 379 – 17 January 395 Born on 11 January 347 in Spain, Theodosius was an aristocrat and military leader, and later brother-in-law of Gratian, who appointed him as emperor of the East in 379 and gave him charge of Macedonia and Dacia. During his reign, Theodosius made Nicene Christianity the official religion of the state. He reunited the whole Empire after defeating Eugenius at the Battle of the Frigidus, in September 394. Theodosius died of a fever at Milan in 395, and his two sons, Honorius and Arcadius, became the emperors of the West and East, splitting power between them. Arcadius 17 January 395 – 1 May 408 Born in 377/378, Arcadius was the eldest son of Theodosius I and upon the latter's death in 395, the Roman Empire was permanently divided between the Eastern Roman Empire—later referred to as the Byzantine Empire—and the Western Roman Empire with Arcadius becoming Byzantine emperor in the East while his younger brother Honorius became emperor in the West; both were manipulated by court officials and did not possess their father's leadership abilities. After contracting an illness, Arcadius died in 408. Theodosius II"the Calligrapher" 1 May 408 – 28 July 450 Born on 10 April 401, he was the only son of Arcadius and Eudoxia. Theodosius II succeeded the throne in 408 upon the death of his father. Because he was a minor, the praetorian prefect Anthemius was essentially regent from 408 to 414, but Theodosius II's elder sister Pulcheria played a critical role as regent and co-ruler during his early years. Theodosius II was known for his mild and scholarly temperament. He had a keen interest in theology, astronomy, and calligraphy, and was reportedly well educated. His long reign was marked by significant legal, administrative, and theological developments. One of the most enduring legacies of his reign was the construction of the Theodosian Walls. These massive fortifications protected the capital for over a millennium and are regarded as one of the greatest defensive structures of antiquity. Theodosius II strongly supported Nicene Christianity and convened the Council of Ephesus in 431 CE, which declared the Virgin Mary as Theotokos ("God-bearer") and condemned the theology of Nestorianism. He also commissioned the Theodosian Code, a comprehensive compilation of Roman laws published in 438; this codex organized and systematized the empire's legal framework and influenced later European legal traditions. During his reign, he faced constant threats from the Huns of Attila and negotiated treaties with them, paying substantial tributes to prevent invasions. He married Eudocia, a learned woman of Greek descent, who, like the emperor's sister Pulcheria, became an influential figure in the court. Their marriage produced one daughter, Licinia Eudoxia, who later married Valentinian III, the Western Roman Emperor. Theodosius II died in 450 from injuries sustained after falling off his horse while hunting. Marcian 25 August 450 – 27 January 457 Born in 396. A soldier and politician, he became emperor after being wed by the Augusta Pulcheria, sister of Theodosius II, following the latter's death. Died of gangrene.
Leonid dynasty (457–518)