"Roman Emperor" is the title historians use to refer to rulers of the Roman Empire, after the epoch conventionally named the Roman Republic. In ancient Rome there was no actual title of "Roman Emperor", and there was never a single office corresponding to it. Rather, the title "Roman Emperor" is a convenient shorthand for a complicated collection of offices and powers.
Discussion of Roman Emperors involves a high degree of historian's editorial discretion, for the Romans themselves did not share the modern understanding of the monarchical concepts of "empire" and "emperor". The Roman Empire had kept all the political institutions and traditions of the Roman Republic, including the Senate and assemblies.
In general, the Emperors cannot truly be described as "de jure" rulers (nominally the Emperor was merely primus inter pares), and many were not "de facto" rulers either (Emperors were frequently themselves figureheads for powerful bureaucrats, functionaries, women, and generals).
The present article discusses the nature of the imperial dignity, and its dynastic development throughout the history of the Empire.
There was no constitutional office of "Roman emperor" (the first person actually to bear that title was Michael I "Rhangabes" in the early 9th Century, who was styled Basileys Rhomai˘n, "Emperor of the Romans" - if appreciating that by that time the meaning of "Basileys" had moved from "King" to "Emperor"), nor any title or rank directly analogous to the title of "emperor"; all the titles traditionally associated with the Emperor had pre-existing, Republican meanings. "Roman Emperor" is a convenient shorthand used by historians to express the much more complicated nature of being the "First Man" in the Roman state, and as a result there are many differing opinions as to precisely who was Emperor when, and how many Emperors there were.
The emperor's legal authority derived from the extraordinary concentration of individual powers and offices extant in the Republic rather than from a new political office (emperors regularly had themselves elected to the consulship and the censorate); the emperor actually held the non-"imperial" offices of princeps senatus (parliamentary leader of the Senate) and pontifex maximus (chief priest of the Roman state religion; lit. "greatest bridge-maker"), both of which had existed for hundreds of years before the Empire. (Gratian was the last emperor to be pontifex maximus; he surrendered the pontificate maximus in 382 to Siricius and it permanently became an auxiliary honour of the Bishop of Rome.)
However, these offices only provided great dignitas (personal prestige) and auctoritas (influence or clout); the emperor's powers derived from the fact that he held ad personam (i.e. without holding office) both imperium maius (greater power or command) and tribunicia potestas (tribunician power). As a result, he formally outranked the provincial governors and the ordinary magistrates (magistratus ordinarii), had the right to enact capital punishment, could command obedience of private citizens (privati), enjoyed personal inviolability (sacrosanctitas), could rescue any plebeian from the hands of any patrician magistrate (ius auxiliandi), and interpose his veto on any act or proposal of any magistrate, including the tribunes of the people (ius intercessio).
"Emperor" was not a magistracy or office of state (note that there was no formally prescribed "uniform" such as those of curule magistrates, senators, and knights; later emperors were distinguished by wearing togae purpurae, purple togas -- hence the phrase "to don the purple" for the assumption of imperial dignity), nor was there even a regular title until the 3rd century. The titles customarily associated with the imperial dignity are imperator ("commander", lit. "one who prepares against"), which emphasises the emperor's military supremacy, caesar, which was originally a name but came to be used to refer to the designated heir (as Nobilissimus Caesar, "Most Noble Caesar") and was retained upon accession, and augustus ("majestic" or "venerable"), which was adopted upon accession (the three titles were rendered in Greek as autokrat˘r, kaisar, and augustos or sebastos respectively). After Diocletian established the Tetrarchy, caesar designated the two junior sub-emperors and augustus the two senior emperors.
The Emperors of the first lineages are rather to be considered as quasi-head of state. As princeps senatus (lit., "first man of the senate"), the Emperor could receive foreign embassages to Rome (but for example Tiberius saw that as a typical task for any group of senators not including himself). All in all, by analogy, in modern terms these early Emperors would tend to be identified as chiefs of state. The office of princeps senatus, however, was not a magistracy and did not own imperium; in terms of the modern Westminster system, this is approximately comparable to diplomatic agents being accredited to the Leader of the House (the consuls functioned as a sort of hybrid between the Speaker of the House and the Prime Minister). At some points in the Empire's history, the Emperor's power was only nominal; powerful praetorian prefects and masters of the soldiers (and even at one point Imperial mothers and grandmothers) occasionally acted as the true source of power (also called "emperors who weren't").
The word princeps (plu. Principes), meaning "first citizen", was a republican term used to denote the leading citizen(s) of the state. It was a purely honorific title with no attached duties or powers. It was the title most preferred by Augustus as it's use implies only primacy, as opposed to imperator which implies dominance. Princeps, because of it's republican connotation, was most commonly used to refer to the emperor in Latin (although the emperor's actual constitutional position was essentially "pontifex maximus with tribunician power and imperium superceding all others") as it was in keeping with the facade of the restored republic; the Greek word basileus ("king") was modified to be synonymous with emperor (and primarily came into favour after the reign of Heraclius) as the Greek had no republican sensibility and openly viewed the emperor as a monarch. In the era of Diocletian and beyond, princeps fell into disuse and was replaced with dominus ("lord"); later emperors used the formula Imperator Caesar NN. Pius Felix (Invictus) Augustus. The use of princeps and dominus broadly symbolise the differences in the Empire's government, giving rise to the era designations "Principate" and "Dominate".
The first Roman Emperor
In the discussion of who was the first Roman Emperor one has to understand that at the end of the Roman Republic there was no new, and certainly not a single, title created with which to indicate the individual who had the supreme power as a monarch. In so far as Emperor could be seen as the English translation of imperator, then yes, Julius Caesar had been an emperor, like several Roman generals before him. Instead, by the end of the civil wars in which Julius Caesar had led his armies, it became clear on the one hand that there was certainly no consensus to return to the Kingdom, and that on the other hand the situation where several officials, bestowed with equal power by the senate, fought one another had to come to an end.
In order to realise that monarchy-without-naming-it Julius Caesar, and a few years later Octavian in an even more subtle and gradual way, worked towards (1) accumulating offices and titles that were of the highest importance in the Republic, (2) making the power attached to these offices permanent, and (3) preventing anyone with similar aspirations from accumulating or maintaining power for themselves.
In that way Julius Caesar had gone a considerable part of the road: He held the Republican offices of consul (four times) and dictator (five times), was appointed perpetual dictator (dictator perpetuus) in 45 BC, had been "pontifex maximus" for several decades and had handsomely prepared for his deification (see Imperial cult). While he was the last dictator of the Republic, he died several years before the final collapse of the traditional Republican system, to be replaced by the system modern historians call the Principate.
By the time of his assassination in 44 BC Julius Caesar was the most powerful man in Rome. But if being "princeps" is seen as the determinating office he should have held for modern historians to call him Emperor, then no, he was not Emperor. Still, he realised something that only a monarch could achieve, but what would only become evident many decades after his death: he had made his high power in the republic hereditary, by his will, in which he had appointed Octavian as his only heir. But not until over a decade after Caesar's death did Octavian achieve supreme power, after the civil wars first avenging Caesar's murder, then the step-by-step process of neutralising his fellow triumvirs, culminating in his victory over Mark Antony and Cleopatra.
When then did Octavian become Emperor? In fact there was no single instant at which he did. Was it when he became Pontifex Maximus? Was it when he was acclaimed Augustus (more a solemn and official nickname than a "title" when he got it)? Was it when he became "princeps"? Was it when the Senate ordained that he held the "tribunicia potestas" ("power of a tribune") without needing to be one of the tribunes? Was it when he started to use Imperator as a praenomen? Note that all this time the organisation of the state remained the same as during the res publica. Even at Augustus' death, some later historians like Tacitus would say, it might have been possible to return to the republic properly, without even needing to change anything, if there had been a real will to accomplish that (that is, by not allowing Tiberius to accumulate the same powers, which he did, however, very quickly). Even Tiberius continued to go to great lengths to keep the "republican" governement system untouched.
The historians of the first centuries saw the continuity in the first place: if a hereditary monarchy-not-by-kings existed after the republic, it had started with Julius Caesar. In this sense Suetonius wrote of The Twelve Caesars, meaning the emperors from Julius Caesar to the Flavians included (where after Nero the inherited name had turned into a title). Most more recent history books, however, noting that immediately after the assassination of Julius Caesar, the Roman State had in all respects returned to the republic and that the second Triumvirate could hardly be called a monarchy, see Augustus as the first "emperor" in the proper sense and (somewhat arbitrarily) say he became emperor when he "restored" power to the senate and people and was given the name Augustus in 27 BC.
The Fall of the West
By the end of the Third century, taking a few steps, the Roman Empire was split in a Western and an Eastern part, each with their own Emperors (and/or Caesars). In the West, which included Rome, the succession of Emperors had stopped by the end of the Fifth century, kicking off the period known as the Middle Ages
The line of Roman emperors in the East continues unbroken until the fall of Constantinople in 1453 under Constantine XI Palaeologos. These emperors eventually normalised the imperial dignity into the modern conception of an emperor, incorporated it into the constitutions of the state, and adopted the aforementioned title Basileys Rhomai˘n ("Emperor of the Romans"; these Emperors ceased to use Latin as the language of state after Heraclius). Historians have customarily treated the state of these later Eastern Emperors under the name "Byzantine Empire", though Byzantine is not a term that the Byzantines ever used to describe themselves.
New Western lineage
The concept of the Roman Empire was renewed in the West with the coronation of the king of the Franks, Charlemagne, as Roman emperor by the Pope on Christmas Day, 800. This line of Roman emperors was actually generally German rather than Roman, but maintained their Romanness as a matter of principle; it lasted until 1806 when Francis II dissolved the Empire during the Napoleonic Wars. These emperors used a variety of titles (most frequently "Imperator Augustus") before finally settling on Imperator Romanus Electus ("Elected Roman Emperor"). Historians customarily assign them the title "Holy Roman Emperor", which has a basis in actual historical usage, and treat their "Holy Roman Empire" as a separate institution.
Titles, Positions, and Powers
Although these are the commonest offices, titles, and positions, one should note that not all Roman Emperors used them, nor were all of them used at the same time. The consular and censorial offices especially were not an integral part of the Imperial dignity, and were usually held by persons other than the reigning Emperor.
Augustus (also "Augoustos" or "Sebastos"), "Majestic" or "Venerable"; an honorific cognomen exclusive to the emperor
Autokratôr, "Autocrat" (lit. "Self-ruler"); Greek title equivalent to imperator i.e. Commander-in-Chief
Basileus, Greek title meaning king, popularly used in the east to refer to the emperor; a formal title of the Roman emperor beginning with Heraclius
Caesar (also "Kaisar" or "Nobilissimus Caesar"), "Caesar" or "Most Noble Caesar"; an honorific name later used to identify an Emperor-designate
Censor, a Republican office with a five year term and one coequal officeholder
Consul, the highest magistracy of the Roman republic with a one year term and one coequal officeholder
- Dominus, "Lord" or "Master"; an honorific title popular in the Empire's middle history
Imperator, "Commander" or "Commander-in-Chief"; a victory title taken on accession to the purple and after a major military victory; the praenomen of most Roman emperors
- Imperium maius, "greater imperium"; absolute power to a degree greater than any other, including power of enacting capital punishment
- Invictus, "Unconquered"; an honorific title
Pater Patriae, "Father of the Fatherland"; an honorific title
- Pius Felix, "Pious and Blessed" (lit. "Dutiful and Happy"); an honorific title
Pontifex Maximus, "Supreme Pontiff" or "Chief Priest" (lit. "Greatest Bridgemaker"); a title and office of Republican origin - could not be used by "Catholic" Emperors, while by that time only the pope had a claim on the title of highest religious authority.
Princeps, "First Citizen" or "Leading Citizen"; an honorific title denoting the status of the emperor as first among equals
- Princeps Iuventatis, "Prince of Youth"; an honorific title awarded to a presumptive Emperor-designate
Princeps Senatus, "First Man of the Senate" a Republican office with a five year term
Tribunicia potestas, "tribunician power"; the powers of a tribune of the people including sacrosanctity and the veto
The lineages and epochs
In the listings of Roman Emperors below, the common name is given first, followed by the more formal name adopted upon accession to the purple, the name given at birth, and the years of his reign. So-called victory titles and other titles not forming an integral part of the name (Pontifex Maximus, Princeps Senatus, Pater Patriae, &c.) are not listed. Co-Emperors are listed in inferior text, along with notes identifying senior Emperors who had hitherto served as co-Emperors. Following abbreviations are used:
- A. - Aulus
- Aug. - Augustus (as a title)
- C. - Gaius
- Germ. - Germanicus
- Imp. - Imperator
- L. - Lucius
- M. - Marcus
- Max. - Maximus
- Nob. - Nobilissimus
- P. - Publius
- P.F. - Pius Felix
- Princ. Iuv. - Princeps Iuventutis
- Q. - Quintus
- Ser. - Servius
- T. - Titus
- Ti. - Tiberius
- Main article: Roman Emperor (Principate)
The nature of the Imperial office and the Principate was established under Julius Caesar's heir and posthumously adopted son, Caesar Augustus, and his own heirs, the descendants of his wife Livia from her first marriage to a scion of the distinguished Claudian clan. This Julio-Claudian dynasty came to an end when the emperor Nero—a great-great-grandson of Augustus through his daughter and of Livia through her son—was deposed in AD 68.
Nero was followed by a succession of usurpers throughout 69, commonly called the "Year of the Four Emperors". The last of these, Vespasian, established his own Flavian dynasty. Nerva, who replaced the last Flavian emperor, Vespasian's son Domitian, in 96, was elderly and childless, and chose therefore to adopt an heir, Trajan, from outside his family. When Trajan acceded to the purple he chose to follow his predecessor's example, adopting Hadrian as his own heir, and the practise then became the customary manner of imperial succession for the next century, producing the "Five Good Emperors" and the Empire's period of greatest stability.
The last of the Good Emperors, Marcus Aurelius, chose his natural son Commodus as his successor rather than adopting an heir. Commodus's misrule led to his murder on 31 December 192, following which a brief period of instability quickly gave way to Septimius Severus, who established the Severan dynasty which, except for an interruption in 217-218, held the purple until 235.
- Main article: Roman Emperor (Crisis of the Third Century)
The accession of Maximinus Thrax marks both the close and the opening of an era. It was one of the last attempts by the increasingly impotent Roman Senate to influence the succession. Yet it was the first time that a man had achieved the purple while owing his advancement purely to his military career; both Vespasian and Septimius Severus had come from noble or middle class families, while Thrax was a born commoner. He never visited the city of Rome during his reign, which marks the beginning of a series of "Barracks Emperors " who came from the army. Between 232 and 285 over a dozen emperors achieved the purple, but only Valerian and Carus managed to secure their own sons' succession to the throne; both dynasties died out within two generations.
- Main article: Roman Emperor (Dominate)
The accession to the purple on November 20, 284, of Diocletian, the lower-class, Greek-speaking Dalmatian commander of Carus's and Numerian's household cavalry (protectores domestici), marked a major departure from traditional Roman constitutional theory regarding the Emperor, who was nominally first among equals; Diocletian introduced Oriental despotism into the Imperial dignity. Whereas before Emperors had worn only a purple toga (toga purpura) and been greeted with deference, Diocletian wore jewelled robes and shoes, and required those who greeted him to kneel and kiss the hem of his robe (adoratio). In many ways, Diocletianus was the first monarchical Emperor, and this is symbolised by the fact that the word dominus ("Lord") rapidly replaced princeps as the favoured word for referring to the Emperor. Significantly, neither Diocletian nor his co-Emperor Maximian spent much time in Rome after 286, establishing their Imperial capitals at Nicomedia and Mediolanum (modern Milan), respectively.
Diocletian established the Tetrarchy, a system by which the Roman Empire was divided into East and West, with each having an Augustus to rule over it and a Caesar to assist him. The Tetrarchy ultimately degenerated into civil war, but the eventual victor, Constantine the Great, restored Domitian's system of dividing the Empire into East and West. He kept the East for himself and founded his city of Constantinople as its new capital.
The dynasty Constantine established also was soon swallowed up in civil war and court intrigue until it was replaced, briefly, by Julian the Apostate's general Jovian and then, more permanently, by Valentinian I and the dynasty he founded in 364. Though he was a soldier from a low middle class background, Valentinian was not a Barracks Emperor ; he was elevated to the purple by a conclave of senior generals and civil officials.
The Late Empire
- Main article: Roman Emperor (Late Empire)
Theodosius I acceded to the purple in the East in 379 and in the West in 394. He outlawed paganism and made Christianity the Empire's official religion. He was the last Emperor to rule over a united empire; the distribution of the East to his son Arcadius and the West to his son Honorius after his death in 395 represented a permanent division.
In the West, the office of Emperor soon degenerated into being little more than a puppet of a succession of Germanic tribal kings, until finally the Heruli Odoacer simply overthrew Emperor Romulus Augustulus in 476 and assumed the title "King of Italy". Though during his own lifetime Odoacer maintained the legal fiction that he was actually ruling Italy as the viceroy of the Emperor in Constantinople, Zeno, historians mark 476 as the traditional date of the fall of the Roman Empire in the West. In the East, the Empire continued as the Byzantine Empire until the fall of Constantinople to the Ottoman Turks in 1453.
- For rulers of Italy after Romulus "Augustulus" and Julius Nepos, see list of barbarian kings.
- For Roman Emperors in the West after Romulus "Augustulus" and Julius Nepos, see list of "Holy Roman Emperors".
- See also list of "Byzantine Emperors".
- Chronicle of the Roman Emperors: The Reign-by-Reign Record of the Rulers of Imperial Rome by Chris Scarre, (c) 1995 Thames and Hudson Ltd, London.