Western Roman Empire
|Roman Empire, Western Part
|Division of the Roman Empire|
Senatus Populusque Romanus
The Western Roman Empire at its greatest extent cca. AD 395
|Religion||Roman religion and later Christianity|
|-||395||Flavius Anicius Hermogenianus Olybrius, Flavius Anicius Probinus|
|-||476||Basiliscus, Flavius Armatus|
|Historical era||Late Antiquity|
|-||Division of Diocletianus||285|
|-||Division after Constantine I||337|
|-||Division by Valentinian I||364|
|-||Division after Theodosius I||395|
|-||Deposition of Romulus Augustus||476|
|-||Assassination of Julius Nepos||480|
|-||395||2,000,000 km² (772,204 sq mi)|
The Western Roman Empire was the western half of the Roman Empire, the other half being the Eastern Roman Empire or Byzantine Empire. Administrative division of the sprawling Empire into a Western and Eastern half with co-emperors for each began under Diocletian in 285 and was periodically abolished and recreated for the next two centuries until final abolishment by the Byzantine emperor Zeno in 480. By that time there was little effective control left in the Western Empire.
A Western Roman Empire existed intermittently in several periods between the 3rd and 5th centuries, after Diocletian's Tetrarchy and the reunifications associated with Constantine the Great and Julian the Apostate (324–363). Theodosius I divided the Empire upon his death (in 395) between his two sons. Eighty-five years later, Zeno would recognize the reality of the Western Empire's reduced domain (Imperial control had been lost over even the Italian Peninsula) after the death of Western Emperor Julius Nepos and rule as sole emperor.
The rise of Odoacer of the Foederati to rule over Italy in 476 was popularized by eighteenth century historian Edward Gibbon as a demarcating event for the end of the Western Empire and is sometimes used to mark the transition from Antiquity to the Middle Ages.
The ongoing struggle between the rising Papacy and the retreating empire led the Pope to unilaterally declare the Frankish King Charlemagne to be the successor of the Western Emperors in 800. This new imperial line would evolve in time into the Holy Roman Empire, which revived the imperial title but was otherwise in no meaningful sense an extension of Roman traditions or institutions. After 924 it was also a primarily Germanic empire that contained little of the former territory of the Western Roman Empire.
As the Roman Republic expanded, it reached a point where the central government in Rome could not effectively rule the distant provinces. Communications and transportation were especially problematic given the vast extent of the Empire. News of invasion, revolt, natural disaster, or epidemic outbreak was carried by ship or mounted postal service, often requiring much time to reach Rome and for Rome's orders to be realized in the province of origin. For this reason, provincial governors had de facto rule in the name of the Roman Republic.
Prior to the establishment of the Empire, the territories of the Roman Republic had been divided among the members of the Second Triumvirate: Mark Antony, Octavian and Marcus Aemilius Lepidus. Antony received the provinces in the East: Achaea, Macedonia and Epirus (roughly modern Greece, Albania and the coast of Croatia), Bithynia, Pontus and Asia (roughly modern Turkey), Syria, Cyprus, and Cyrenaica. These lands had previously been conquered by Alexander the Great; thus, much of the aristocracy was of Greek origin. The whole region, especially the major cities, had been largely assimilated into Greek culture, Greek often serving as the lingua franca.
Octavian obtained the Roman provinces of the West: Italia (modern Italy), Gaul (modern France), Gallia Belgica (parts of modern Belgium, the Netherlands and Luxembourg), and Hispania (modern Spain and Portugal). These lands also included Greek and Carthaginian colonies in the coastal areas, though Celtic tribes such as Gauls and Celtiberians were culturally dominant. Lepidus received the minor province of Africa (roughly modern Tunisia). Octavian soon took Africa from Lepidus, while adding Sicilia (modern Sicily) to his holdings.
Upon the defeat of Mark Antony, a victorious Octavian controlled a united Roman Empire. While the Roman Empire featured many distinct cultures, all were often said to experience gradual Romanization. While the predominantly Greek culture of the East and the predominantly Latin culture of the West functioned effectively as an integrated whole, political and military developments would ultimately realign the Empire along those cultural and linguistic lines.
 Rebellions, uprisings, and political developments
Minor rebellions and uprisings were fairly common events throughout the Empire. Conquered tribes or cities would revolt, and the legions would be detached to crush the rebellion. While this process was simple in peacetime, it could be considerably more complicated in wartime, as for example in the Great Jewish Revolt.
In a full-blown military campaign, the legions, under generals such as Vespasian, were far more numerous. To ensure a commander's loyalty, a pragmatic emperor might hold some members of the general's family hostage. To this end, Nero effectively held Domitian and Quintus Petillius Cerialis, governor of Ostia, who were respectively the younger son and brother-in-law of Vespasian. The rule of Nero ended only with the revolt of the Praetorian Guard, who had been bribed in the name of Galba. The Praetorian Guard, a figurative "sword of Damocles", were often perceived as being of dubious loyalty. Following their example, the legions at the borders increased participation in the civil wars.
The Parthian Empire, in the East, on the other hand, was too remote and powerful to be conquered. Any Parthian invasion was confronted and usually defeated, similarly, Parthians repelled some attempts of Roman invasion, however, even after successful wars of conquest - such as those implemented by Trajan and Septimius Severus - those distant territories were forsaken to prevent unrest and also to ensure a more healthy and lasting peace with the Persians.
Controlling the western border of Rome was reasonably easy because it was relatively close and also because of the disunity between the Germanic foes, however, controlling both frontiers altogether during wartime was difficult. If the emperor was near the border in the East, chances were high that an ambitious general would rebel in the West and vice-versa. This wartime opportunism plagued many ruling emperors and indeed paved the road to power for several future emperors.
 Economic stagnation in the West
Rome and the Italian peninsula began to experience an economic slowdown as industries and money began to move outward. By the beginning of the 2nd century AD, the economic stagnation of Italia was seen in the provincial-born Emperors, such as Trajan and Hadrian. Economic problems increased in strength and frequency.
 Crisis of the 3rd century
Starting on 18 March 235, with the assassination of the Emperor Alexander Severus, the Roman Empire sank into a 50-year civil war, known today as the Crisis of the Third Century. The rise of the bellicose Sassanid dynasty in Parthia posed a major threat to Rome in the east. Demonstrating the increased danger, Emperor Valerian was captured by Shapur I in 259. His eldest son and heir-apparent, Gallienus, succeeded and took up the fight on the eastern frontier. Gallienus' son, Saloninus, and the Praetorian Prefect Silvanus were residing in Colonia Agrippina (modern Cologne) to solidify the loyalty of the local legions. Nevertheless, Marcus Cassianius Latinius Postumus - the local governor of the German provinces - rebelled; his assault on Colonia Agrippina resulted in the deaths of Saloninus and the prefect. In the confusion that followed, an independent state known as the Gallic Empire emerged.
Its capital was Augusta Treverorum (modern Trier), and it quickly expanded its control over the German and Gaulish provinces and over all of Hispania and Britannia. It had its own senate, and a partial list of its consuls still survives. It maintained Roman religion, language, and culture, and was far more concerned with fighting the Germanic tribes than other Romans. However, in the reign of Claudius Gothicus (268 to 270), large expanses of the Gallic Empire were restored to Roman rule. At roughly the same time, several eastern provinces seceded under the Palmyrene Empire, under the rule of Queen Zenobia.
In 272, Emperor Aurelian finally managed to reclaim Palmyra and its territory for the empire. With the East secure, his attention was turned to the West, taking the Gallic Empire a year later. Because of a secret deal between Aurelian and Gallic Emperor Tetricus I and his son Tetricus II, the Gallic army was swiftly defeated. In exchange, Aurelian spared their lives and gave the two former rebels important positions in Italy.
The external borders were mostly stable for the remainder of the Crisis of the Third Century, although, between the death of Aurelian in 275 and the accession of Diocletian ten years later, at least eight emperors or would-be emperors were killed, many assassinated by their own troops.
Under Diocletian, the political division of the Roman Empire began. In 285, he promoted Maximian to the rank of Augustus (Emperor) and gave him control of the Western regions of the Empire. In 293, Galerius and Constantius Chlorus were appointed as their subordinates (Caesars), creating the First Tetrarchy. This system effectively divided the Empire into four major regions and created separate capitals besides Rome as a way to avoid the civil unrest that had marked the 3rd century. In the West, the capitals were Maximian's Mediolanum (now Milan) and Constantius' Trier. In the East, the capitals were Sirmium and Nicomedia. On 1 May 305, the two senior Augusti stepped down, and their respective Caesars were promoted to Augusti and appointed two new Caesars, thus creating the Second Tetrarchy.
 Constantine the Great
The system of the Tetrarchy quickly ran aground when the Western Roman Empire's Constantius died unexpectedly in 306, and his son Constantine the Great was proclaimed Augustus of the West by the legions in Britain. A crisis followed as several claimants attempted to rule the Western half. In 308, the Augustus of the East, Galerius, arranged a conference at Carnuntum which revived the Tetrarchy by dividing the West between Constantine and a newcomer named Licinius. Constantine was far more interested in conquering the whole empire. Through a series of battles in the East and the West, Licinius and Constantine stabilized their respective parts of the Roman Empire by 314, and began to compete for sole control of a reunified state. Constantine emerged victorious in 324 after the surrender and murder of Licinius following the Battle of Chrysopolis.
The Tetrarchy ended, but the idea of dividing the Roman Empire between two emperors had been validated. Very strong emperors would reunite it under their single rule, but with their death the Roman Empire would be divided again and again between the East and the West.
 Second division
Constantius was born in 317 at Sirmium, Pannonia. He was the third son of Constantine the Great, and second by his second wife Fausta, the daughter of Maximian. Constantius was made Caesar by his father on 13 November 324. The Roman Empire was under the rule of a single Emperor, but, with the death of Constantine in 337, civil war erupted among his three sons, dividing the Empire into three parts. The West was unified in 340 under Constans, who was assassinated in 350 under the order of the usurper Magnentius; after Magnentius lost the Battle of Mursa Major and committed suicide, a complete reunification of the whole Empire occurred in 353, with Constantius II.
Constantius II focused most of his power in the East and is regarded as the first emperor of the Byzantine Empire. Under his rule, the city of Byzantium - only recently re-founded as Constantinople - was fully developed as a capital. In 361, Constantius II became ill and died, and Constantius Chlorus' grandson Julian, who had served as Constantius II's Caesar, assumed power. Julian was killed in 363 in the Battle of Samarra against the Persian Empire and was succeeded by Jovian, who ruled only until 364.
 Final division
Following the death of Jovian, Valentinian I emerged as Emperor in 364. He immediately divided the Empire once again, giving the eastern half to his brother Valens. Stability was not achieved for long in either half, as the conflicts with outside forces intensified. In 376, the Visigoths, fleeing before the Ostrogoths, who in turn were fleeing before the Huns were allowed to cross the river Danube and settle into the Balkans by the Eastern government. Mistreatment caused a full-scale rebellion, and in 378 they inflicted a crippling defeat on the Eastern Roman field army in the Battle of Adrianople, in which Valens also died. After plundering the countryside, they officially became foederati, thus remaining a destabilizing element, as well as a stabilizing element within the Empire.
More than in the East, there was also opposition to the Christianizing policy of the Emperors in the western half of the Empire. In 379, Valentinian I's son and successor Gratian declined to wear the mantle of Pontifex Maximus, and in 382 he rescinded the rights of pagan priests and removed the pagan altar from the Roman Curia, a decision which caused dissatisfaction among the traditionally pagan aristocracy of Rome. Theodosius I later decreed a ban on the native paganism, further enforcing Christianity as the official state religion.
The political situation was unstable. In 383, a powerful and popular general named Magnus Maximus seized power in the West and forced Gratian's half-brother Valentinian II to flee to the East for aid; the Eastern Emperor Theodosius I promptly restored him to power. In 392, the Frankish and pagan magister militum Arbogast assassinated Valentinian II and proclaimed an obscure senator named Eugenius as Emperor.
The rebellion was overcome in 394 by Theodosius I, who then briefly ruled a united Empire until his death in 395. He was the last Emperor to rule both parts of the Roman Empire; his older son Arcadius inherited the eastern half while the younger Honorius got the western half. Both were still minors. Honorius was placed under the tutelage of the half-Roman/half-barbarian magister militum Flavius Stilicho while Rufinus became the power behind the throne in the east. Rufinus and Stilicho were rivals, and disagreements between the eastern and western courts regarding ownership of Illyricum were skillfully exploited by the Gothic king Alaric I who again rebelled following the death of Theodosius I.
Stilicho ably defended Italy against the invading Goths, but failed to control the Vandals, Alans, and Suevi who invaded Gaul in numbers. Stilicho became a victim of court intrigues in Ravenna - where the Western Imperial court resided starting in 402 - and was subsequently executed for high treason in 408. While the East began a slow recovery and consolidation, the West began to collapse entirely.
 Economic factors
The West, less urbanized with a spread-out populace, may have experienced an economic decline throughout the Late Empire in some provinces. Southern Italy, northern Gaul (except for large towns and cities) to some extent Spain and the Danubian areas may have suffered. The East was not so destitute, especially as Emperors like Constantine the Great and Constantius II had invested heavily in the eastern economy. As a result, the Eastern Empire could afford large numbers of professional soldiers and augment them with mercenaries, while the Western Roman Empire could not afford this to the same extent. Even in major defeats, the East could, certainly not without difficulties, buy off its enemies with a ransom.
The political, economic and military control of the Eastern Empire's resources remained safe in Constantinople, which was well fortified and located at the crossroads of several major trade and military routes. In contrast, the Western Empire was more fragmented. Its capital was transferred to Ravenna in 402 largely for defensive reasons, and it had easy of access to the imperial fleet of the Eastern Empire but was isolated in other aspects as it was surrounded by swamps and marshes. The economic power remained focused on Rome and its hyper-rich senatorial aristocracy which dominated much of Italy and Africa in particular. After Gallienus banned senators from army commands in the mid-3rd century, the senatorial elite lost all experience of—and interest in—military life. In the early 5th century the wealthy landowning elite of the Roman Senate largely barred its tenants from military service, but it also refused to approve sufficient funding for maintaining a sufficiently powerful mercenary army to defend the entire Western Empire. The West's most important military area had been northern Gaul and the Rhine frontier in the 4th century, when Trier frequently served as the capital of the Empire and many leading Western generals were Barbarians. After the civil war in 394 between Theodosius I and Eugenius, the new Western government installed by Theodosius I increasingly had to divert military resources from Britain and the Rhine to protect Italy. This, in turn, led to further rebellions and civil wars because the Western imperial government was not providing the military protection the northern provinces expected and needed against the barbarians.
The Western Empire's resources were much limited, and the lack of available manpower forced the government to rely ever more on confederate barbarian troops operating under their own commanders, where the Western Empire would often have difficulties paying. In certain cases deals were struck with the leaders of barbaric mercenaries rewarding them with land, which led to the Empire's decline as less land meant there would be even less taxes to support the military.
As the central power weakened, the State gradually lost control of its borders and provinces, as well as control over the Mediterranean Sea. Roman Emperors tried to maintain control of the sea, but, once the Vandals conquered North Africa, imperial authorities had to cover too much ground with too few resources. The loss of the African provinces might have been the worse reversal on the West's fortunes, since they were among its wealthiest territories and supplied the essential grain imports to Italy. In many places, the Roman institutions collapsed along with the economic stability. In some regions, such as Gaul and Italy, the settlement of barbarians on former Roman lands seems to have caused relatively little disruption.
 Sack of Rome and fall of the Western Roman Empire
Remaining as emperor after the death of Stilicho in 408, Honorius reigned until his own death in 423. His reign was filled with usurpations and invasions. In 410, Rome was sacked by Alaric's forces. This event made a great impression on contemporaries, as this was the first time since the Gallic invasions of the 4th century BC that the city had fallen to a foreign enemy. Under Alaric's successors, the Goths then settled in Gaul (412–418), from where they operated as Roman allies against the Vandals, Alans, and Suevi in Spain, and against the usurper Jovinus (413). Meanwhile, another usurper, Constantine (406–411), had stripped Roman Britain of its defenses when he crossed over to Gaul in 407, leaving the Romanized population subject to invasions, first by the Picts and then by the Saxons, Angli, and the Jutes who began to settle permanently from about 440 onwards.
Honorius' death in 423 was followed by turmoil until the Eastern Roman government with the force of arms installed Valentinian III as Western Emperor in Ravenna, with Galla Placidia acting as regent during her son's minority. After a violent struggle with several rivals, and against Placidia's wish, Aetius rose to the rank of magister militum. Aetius was able to stabilize the Western Empire's military situation somewhat, relying heavily on his Hunnic allies. With their help, he defeated the Burgundians, who had occupied part of southern Gaul after 407, and settled them in Savoy as Roman allies (433). Later that century, as Roman power faded away, the Burgundians extended their rule to the Rhone valley.
Meanwhile, pressure from the Visigoths and a rebellion by Bonifacius, the governor of Africa, induced the Vandals under their king Gaiseric to cross over from Spain in 429. They temporarily halted in Numidia (435) before moving eastward and capturing Carthage, from where they established an independent state with a powerful navy (439). The Vandal fleet became a constant danger to Roman sea trade and the coasts and islands of the western and central Mediterranean.
In 444, the Huns, who had been employed as Roman allies by Aetius, were united under their ambitious king Attila. Turning against their former ally, the Huns became a formidable threat to the Empire. Attila then received a plea for help and the ring of Honoria, the Emperor's sister. Threatening war, he claimed half of the Western Empire's territory as his dowry.
Faced with refusal, he invaded Gaul and was only stopped in the battle of the Catalaunian Plains by a combined Roman-Germanic army led by Aetius. The next year, Attila invaded Italy and proceeded to march upon Rome, but an outbreak of disease in his army, Pope Leo's plea for peace, and reports of a campaign of Marcianus directed at his headquarters in Pannonia induced him to halt this campaign. Attila unexpectedly died a year later (453).
Aetius was slain in 454 by Valentinian, who was then himself murdered by the dead general's supporters a year later. With the end of the Theodosian dynasty, a new period of dynastic struggle ensued. The Vandals took advantage of the unrest and sailed up to Rome, which they plundered in 455.
The instability caused by usurpers throughout the Western Empire helped these tribes in their conquests, and by the 450s the Germanic tribes had become usurpers themselves. During the next twenty years, several Western Emperors were installed by Constantinople, but their authority relied upon barbarian commanders (Ricimer (456–472), Gundobad (473–475)). In 475, Orestes, a former secretary of Attila, drove Emperor Julius Nepos out of Ravenna and proclaimed his own son Romulus Augustus as emperor.
In 476, Orestes refused to grant Odoacer and the Heruli federated status, prompting an invasion. Orestes was killed and Odoacer deposed Romulus Augustus, installed himself as ruler over Italy and sent the Imperial insignia to Constantinople. Although isolated pockets of Roman rule continued even after 476, the city of Rome itself was under the rule of the barbarians, and the control of Rome over the West had effectively ended.
Three rump states continued under Roman rule in some form or another after 476: Julius Nepos controlled Dalmatia until his murder in 480. Syagrius ruled the Domain of Soissons until his murder in 487. Lastly, a Roman-Moor realm survived in north Africa, resisting Vandal incursions, and becoming a part of the Eastern Roman Empire c.533 when Belisarius defeated the Vandals.
 Last Emperor
Julius Nepos still claimed to be Emperor of the West, and ruled a rump state in Dalmatia. He was recognized as such by Eastern Roman Emperor Zeno and by Syagrius, who had managed to preserve Roman sovereignty in an exclave in northern Gaul, known today as the Domain of Soissons.
Odoacer proclaimed himself ruler of Italy and began to negotiate with Zeno. Zeno eventually granted Odoacer patrician status as recognition of his authority and accepted him as his own viceroy of Italy. Zeno, however, insisted that Odoacer had to pay homage to Julius Nepos as the Emperor of the Western Empire. Odoacer accepted this condition and issued coins in the name of Julius Nepos throughout Italy. This, however, was mainly an empty political gesture, as Odoacer never returned any real power or territories to Julius Nepos. The murder of Julius Nepos in 480 prompted Odoacer to invade Dalmatia, annexing it to his Kingdom of Italy.
 Political change after empire fall
The last hope for a reunited Empire came in 493, as Odoacer was replaced by Theodoric the Great, king of the Ostrogoths. Theodoric had been forced to appear subservient to Zeno in order to deal with a dangerous Odoacer. While in principle Theodoric was a subordinate, a viceroy of the Emperor of the East, in fact he was his equal.
Following Theodoric's death in 526, the Western half of the Empire was now fully controlled by Germanic tribes (though many of them continued to recognize Roman law and made claims to continuity), while the Eastern half had established itself under the Justinian dynasty. While the East would make some attempts to recapture the West, the Roman Empire was never reunited.
 Byzantine Reconquest
Throughout Late Antiquity and the early Middle Ages, the Eastern Roman Empire, or the Byzantine Empire, laid claims on areas of the West which had been occupied by several tribes. In the 6th century, the Eastern Roman Empire managed to reconquer large areas of the former Western Roman Empire. The most successful were the campaigns of the generals Belisarius and Narses on behalf of the Eastern Roman Emperor Justinian I from 533 to 554). The Vandal-occupied former Roman territory in North Africa was regained, particularly the territory centered around the city of Carthage. The campaign eventually moved into Italy and the Byzantines reconquered it completely. Minor territories were taken as far west as the southern coast of the Iberian Peninsula. But already in 568, three years after Justinian had died, the Lombards had invaded Italy.
Although some eastern emperors occasionally attempted to reconquer some parts of the West, none were as successful as Justinian. The division between the two areas grew, resulting in a growing rivalry. While the Eastern Roman Empire continued after Justinian, the later Eastern Emperors focused mainly on defending its traditional territory. From the 7th century onwards, the East no longer had the necessary military strength to do anything else, spelling the end of any hope for reunification.
As the Western Roman Empire crumbled, the new Germanic rulers who conquered the provinces upheld many Roman laws and traditions. Many of the invading Germanic tribes were already Christianized, although most were followers of Arianism. They quickly converted to Catholicism, gaining more loyalty from the local Roman populations, as well as the recognition and support of the powerful Catholic Church. Although they initially continued to recognize indigenous tribal laws, they were more influenced by Roman Law and gradually incorporated it as well.
Roman Law, particularly the Corpus Juris Civilis collected by order of Justinian I, is the ancient basis on which the modern Civil law stands. In contrast, Common law is based on the Germanic Anglo-Saxon law.
Latin as a language never really disappeared. It combined with neighboring Germanic and Celtic languages, giving rise to many modern Romance languages such as Italian, French, Spanish, Portuguese, Romanian, Catalan, Occitan, and Romansh.
Latin also influenced Germanic languages such as English, German, and Dutch; all surviving Celtic languages, Albanian, and such Slavic languages as Polish and Czech, and even the non-Indo-European Hungarian. It survives in its "purer" form as the language of the Catholic Church (the Mass was spoken exclusively in Latin until 1969), and was used as a lingua franca between many nations. It remained the language of medicine, law, diplomacy (most treaties were written in Latin), of intellectuals and scholarship.
The Latin alphabet was expanded due to the splits of I into I and J and of U into U, V, and in places (especially Germanic languages and Polish) W; it is the most widely used alphabetic writing system in the world today. Roman numerals continue to be used, but were mostly replaced by Arabic numerals.
The ideal of the Roman Empire as a mighty Christian Empire with a single ruler continued to seduce many powerful rulers. Under the principle of translatio imperii, the Holy Roman Empire explicitly proclaimed itself as the continuation of the Western Roman Empire. The title of the Western Roman Emperor was revived when Charlemagne, King of the Franks and Lombards, was crowned as Emperor of the Romans of the West by Pope Leo III in 800. The status of the Holy Roman Emperor as the rightful Western Roman Emperor in the medieval era was further legitimated by the recognition as "co-emperor" from the Eastern Roman Emperor, who was in direct succession to the ancient Roman Emperors. The Holy Roman Empire continued to regard itself as the successor state of the Western Roman Empire until its downfall in 1806. The French King Louis XIV, as well as French Emperor Napoleon I, among others, also tried to resurrect the Empire, albeit unsuccessfully.
A very visible legacy of the Western Roman Empire is the Roman Catholic Church. The Church slowly began to replace Roman institutions in the West, even helping to negotiate the safety of Rome during the late 5th century. In many cases the only source of law and civil administration was the local bishop, often himself a former governor like St. Ambrose of Milan and St. Germanus of Auxerre. As Rome was invaded by Germanic tribes, many assimilated, and by the middle of the medieval period (c.9th and 10th centuries) the central, western, and northern parts of Europe had been largely converted by the Roman Catholicism and acknowledged the Pope as the Vicar of Christ.
 List of Western Roman Emperors
 Gallic Emperors (259 to 273)
- Postumus: 259 to 268
- Laelianus: 268 Usurper
- Marcus Aurelius Marius: 268
- Victorinus: 268 to 271
- Domitianus: 271 Usurper
- Tetricus I: 271 to 273
- Tetricus II: 271 to 273 Son and co-emperor of Tetricus I
 Tetrarchy (293 to 313)
Augusti are shown with their Caesares and regents further indented
- Maximian: 293 to 305
- Constantius Chlorus: 293 to 305
- Constantius Chlorus: 305 to 306
- Flavius Valerius Severus: 305 to 306
- Flavius Valerius Severus: 306 to 307
- Constantine I: 306 to 313
- Maxentius/Maximian: 307 to 308
- Licinius: 308 to 313
- Maxentius: 308 to 312 Usurper
- Domitius Alexander: 308 to 309 African usurper
 Constantinian dynasty (313 to 363)
- Constantine the Great: 306 to 337 Sole emperor of the empire from 324 to 337
- Constantine II: 337 to 340 Emperor of Gaul, Britannia, and Hispania
- Constantius II: 337 to 361 Emperor of the east from 337 to 353, Sole emperor of the empire from 353 to 360
- Constans I: 337 to 350 Emperor of Italy and Africa 337-340, emperor of the west from 340 to 350
- Magnentius: 350 to 353 Usurper
- Julian: 355 to 363 Emperor of the west from 355 to 361, Sole emperor of the empire from 361 to 363
 Non-dynastic (363 to 364)
- Jovian: 363 to 364
 Valentinian dynasty (364 to 392)
- Valentinian I: 364 to 375
- Gratian: 367 to 375
- Gratian: 375 to 383
- Valentinian II: 375 to 383
- Magnus Maximus: 383 to 388 Usurper
- Valentinian II: 383 to 392
 Non-dynastic (392 to 394)
- Eugenius: 392 to 394
 Theodosian dynasty (394 to 455)
- Theodosius I: 394 to 395 Sole emperor
- Honorius: 395 to 423
- Constantine III: 407 to 411 Usurper
- Priscus Attalus: 409 to 410/414 to 415 Usurper
- Jovinus: 411 to 412 Usurper
- Valentinian III: 423 to 455
- Joannes: 423 to 425 Usurper
 Non-dynastic (455 to 480)
- Petronius Maximus: 455 not recognized in Constantinople
- Avitus: 455 to 456 not recognized in Constantinople
- Ricimer: 456 to 472 Power behind the throne
- Majorian: 457 to 461
- Libius Severus: 461 to 465 not recognized in Constantinople
- Anthemius: 467 to 472
- Olybrius: 472 not recognized in Constantinople
- Glycerius: 473 to 474 not recognized in Constantinople
- Julius Nepos: 474 to 480 In exile 475 to 480
- Romulus Augustus: 475 to 476 not recognized in Constantinople
- Flavius Orestes: 475 to 476 Power behind the throne
 See also
- Taagepera, Rein (1979). "Size and Duration of Empires: Growth-Decline Curves, 600 B.C. to 600 A.D". Social Science History (Duke University Press) 3 (3/4): 24. doi:10.2307/1170959. JSTOR 1170959.
- DiMaio Jr., M. & Frakes, R. 'DIR-Constantius II' from De Imperatoribus Romanis 
- Henning Börm: Das weströmische Kaisertum nach 476. In: Josef Wiesehöfer et al. (eds.), Monumentum et instrumentum inscriptum. Stuttgart 2008, pp. 47–69.
- Neil Christie: The Fall of the Western Roman Empire. London 2011.
- Kaj Sandberg: The So-Called Division of the Roman Empire. Notes On A Persistent Theme in Western Historiography, Arctos 42 (2008), 199-213.
- El Housin Helal Ouriachen, 2009, La ciudad bética durante la Antigüedad Tardía. Persistencias y mutaciones locales en relación con la realidad urbana del Mediterraneo y del Atlántico, Tesis doctoral, Universidad de Granada, Granada.
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- De Imperatoribus Romanis
- Maps of the Roman state according to the Compilation 'notitia dignitatum'