Note that the Emperor was quasi-head of state; as princeps senatus (lit., "first man of the senate"), the Emperor received foreign embassages to Rome, which in modern terms would tend to identify him as chief of state. However, the principate senatus 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 was only nominal quasi-head of state; powerful praetorian prefects and masters of the soldiers (and even at one point Imperial mothers and grandmothers) occasionally acted as what might be called "shadow emperors" (also called "emperors who weren't").
Also note that contrary to popular belief, Gaius Iulius Caesar ("Julius Caesar") was not a Roman emperor. He held the Republican offices of consul (four times) and dictator (five times), and was appointed perpetual dictator (dictator perpetuus) in 45 BC. While he is the last dictator of the Republic, he died several years before the final collapse of the traditional Republican system, to be replaced by the Principate.
There was no constitutional office of "Roman emperor" (the first person actually to bear that title was Mixahl I "Rhangabes in the early IX century, who was styled Basileys Rhomaiτn, "Emperor of the Romans"), 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 consulate and the censorate); the emperor actually held the non-"imperial" offices of princeps senatus (parliamentary leader of the house in 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. (Gratianus 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 (supreme authority 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 III century. The titles customarily associated with the imperial dignity are imperator ("commander", lit. "one who prepares against"), which emphasises the emperor's military supremacy (later particularly ironical in the era of the so-called "Barracks Emperors"), 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 autokratτr, kaisar, and augustos (or sebastos), respectively). When Diocletianus established the Tetrarchy, caesar designated the two junior sub-emperors and augustus the two senior emperors.
The word princeps, from the emperor's office of princeps senatus, 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"); the Greek word basileys ("king") was modified to be synonymous with princeps in the sense of "emperor" (and primarily came into favour after Heraclius defeated the Persian "Great King", or basileys). In the era of Diocletianus 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 line of Roman emperors in the East continues unbroken until the fall of Constantinople in 1453 under Konstantinos 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 Rhomaiτn ("Emperor of the Romans"; these Emperors ceased to use Latin as the language of state after Heraclius). Historians have customarily treated these later Eastern emperors under the non-historical name "Byzantine Empire".
The concept of the Roman Empire was renewed in the West with the coronation of the king of the Franks, Karl I as Roman emperor 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 Franz 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"), and are customarily treated by historians under the title "Holy Roman Emperor", which unlike "Roman Emperor" and "Byzantine Empire" has an actual historical basis.
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.
The Julio-Claudian dynasty was composed of the Iulii Caesares and the Claudii Nerones, two distinguished patrician families in the waning days of the old Republic. The Iulii Caesares rose to absolute power in the Roman state in the person of the paterfamilias, Julius Caesar himself; upon his murder in 44 BC, the majority of his estate passed to his posthumously adopted son, Gaius Octavius, the grandson of Caesar's sister Iulia (per Roman naming convention, Octavius henceforth became called "Gaius Iulius Caesar Octavianus"). Octavianus emerged from a series of civil wars as the sole master of the Roman world, and in January 27 BC was appointed princeps senatus and given the cognomen "Augustus" (L., "Majestic" or "Venerable"); henceforth he styled himself "Imperator Caesar Augustus". He continued to be elected consul ordinarius each year until 23 BC.
Historians customarily mark the "First Settlement" of 27 as inaugurating Caesar Augustus's reign as Emperor. This is generally misleading, as his constitutional position that year was little different from his constitutional position as early as July 32 BC (when he provoked war with Cleopatra VII of Egypt as a means of ridding himself of his rival Marcus Antonius), except that he now held the principate of the senate (an office with chiefly parliamentary and ceremonial functions) and bore an honorific surname. A far more important development was the "Second Settlement" of 23 BC, when Caesar Augustus accepted tribunicia potestas for life and imperium maius proconsulare. Two further developments concluded the establishment of the Imperial dignity: Caesar Augustus accepted imperium consulare on an ad personam basis in 19 BC and was elected pontifex maximus in 13 BC. Thus the Imperial dignity was fully established as the extraordinary concentration of ordinary powers and immunities.
Julio-Claudian Emperors:
Caesar Augustus's third wife Livia Drusilla (subsequently "Iulia Augusta") had previously borne two children by her first husband, Tiberius Claudius Nero: Tiberius and Drusus. Tiberius's second wife was Julia Caesaris, Marcus Agrippa's widow (his first wife had been Vipsania, Agrippa's daughter by his first marriage); Caesar Augustus adopted Tiberius on June 26, 4, whereupon Tiberius himself adopted his brother Drusus's son by Marcus Antonius's daughter, Germanicus Julius Caesar. Germanicus married Vipsania Agrippina, Agrippa's daughter by Julia and Tiberius's stepdaughter, and had by her one surviving son, Gaius "Caligula" ("Bootkins"), and a daughter, Julia Agrippina, whose second husband was Germanicus's brother by blood, Claudius (she was his fourth wife); Agrippina had already borne a son, Lucius, whom Claudius adopted under the name Nero in 40; Nero married Claudius's daughter Octavia in 53.
The year 69 is often called the "Year of the Four Emperors" because it saw four usurperss successively claim the purple. The fourth Emperor is listed in the next section due to dynastic considerations.
The Flavian dynasty was composed of the Flavii Vespasiani, a middle-class family of plebeian stock. A relatively short-lived dynasty of 30 years, the Flavians confirmed the use of "Caesar" to confirm the hereditary nature of the Imperial dignity (Vespasianus gave both his sons this rank, and is said to have informed the Senate that one of his sons would succeed him or no one would). Domitianus made himself extremely unpopular by his autocratic manner, which was a departure from the traditional fiction that the Emperor was merely first among equals (primus inter pares).
Flavian Emperors:
Vespasianus's wife Flavia Domitilla bore him a daughter (Flavia Domitilla) and two sons (Titus and Domitianus).
The Nervan-Antonine dynasty was a largely artificial one, chiefly built out more of adoption than blood relations, as in the Julio-Claudian or Flavian dynasties (the first Emperor of this dynasty was an elderly, childless man, from the noble Cocceii Nervae). The Nervan-Antonine dynasty produced the famous "Five Good Emperors", and the first non-Italian Roman Emperors (viz., the Spaniards Trajanus and Hadrianus). The Nervan-Antonine dynasty also marks the first time that an Emperor (viz., Hadrianus) was depicted with a beard, and one of the first times that a deceased Emperor (viz., Antoninus Pius) was inhumed rather than cremated. Note that the Nervan-Antonine Emperors adopted the regularised style Imperator Caesar NN. Augustus, whereas there had hitherto been considerable variation.
Nervan-Antonine Emperors:
Nerva was a childless bachelor, and as a result adopted the governor of Germania Superior, Trajanus, in October 97. Trajanus's first cousin, once removed, Hadrianus, was his ward and governor of Syria at the time of his guardian's death, and acceded to the purple without having been adopted by his predecessor. Hadrianus himself adopted Antoninus Pius on February 25, 138; at the same time, Antoninus Pius adopted Marcus Aurelius and Lucius Verus. Marcus Aurelius was son of Trajanus's great-grandnephew (and consequently grandson of the half-sister of Hadrianus's wife), and subsequently married Antoninus Pius's daughter Annia Galeria Faustina, and Lucius Verus was son of Lucius Ceionius Commodus, who had been Hadrianus's first choice as Caesar and Emperor-designate. Marcus Aurelius's sixth son (of eight) was Commodus.
In March 193, the Imperial dignity was quite literally and quite openly auctioned off by the mutinous Praetorian Guard, with Titus Flavius Sulpicianus (father-in-law of the slain Emperor) and Marcus Didius Julianus bidding for the Guard's support for the purple.
The short-lived Severan dynasty came into the purple primarily not by vote of the Senate like the Julio-Claudii but rather by the point of the sword like the Flavii. The founder of the dynasty, Lucius Septimius Severus, was descended from a provincial family from North Africa and is reputed to have kept his African accent until his death. To help bolster his hold on power, Septimius Severus identified himself with the cause of the late Pertinax (and incorporated this into his name), and was called by some "the Punic Sulla", a slur simultaneously pointing to his African origins and his utter ruthlessness. The Antonine Constitution of 212 granted full citizenship to all free men in the Empire.
Septimius Severus's second wife Julia Domna bore him two sons, Lucius "Caracalla" ("Long Coat") and Geta. Caracalla was (falsely) rumoured to have fathered a bastard by his first cousin Julia Soaemis (daughter of his maternal aunt Julia Maesa); this rumoured bastard would later become "Elagabalus" (see below).
Although Macrinus and Diadumenianus are listed here as non-dynastic, this is somewhat misleading; Macrinus was Diadumenianus's father. However, as the equestrian family produced no further Emperors, and the second was co-Emperor with the first, it is not being listed as a dynasty. Cassius Dio writes that Macrinus was a Moor from Caesarea; note that he did not style himself "Caesar", but did add "Severus" to his name and inserted Pius Felix before the title "Augustus".
The Severi, in addition to being the second dynasty d'ιpιe, are also the first Roman dynasty to have been restored to the purple. The restoration, however, brought with it a decidedly bizarre character: the first of the restored Severan Emperors, a Syrian historically known as "Elagabalus" (also seen less correctly as "Heliogabalus") was already the hereditary high priest of an Oriental sun god, Elagabal. The restored Severi were also well-known for the autocratic power exercised by three Syrian princesses as ιminence grises, viz., Elagabalus's mother Julia Soaemis and grandmother Julia Maesa, and Alexander Severus's mother Julia Mamaea; these women were in fact Emperors in all but name.
"Elagabalus" was son of Sextus Varius Marcellus, a Syrian, and Julia Soaemis, daughter of Julia Maesa (the younger sister of Julia Domna, wife of Septimius Severus); he was therefore nephew of the late "Caracalla", whose natural son he claimed to be (note that he took the same name as Caracalla upon donning the purple). Elagabalus and Alexander Severus (also seen more correctly as "Severus Alexander") were first cousins; Alexander Severus's mother was Julia Mamaea, another daughter of Julia Maesa.
The accession to the purple of Gaius Julius Verus Maximinus "Thrax ("the Thracian") marks the rise of the first "Barracks Emperor" par excellence. Whereas the previous military Emperors (Vespasianus, Septimius Severus) had come from noble or middle-class plebeian families, Maximinus was born a commoner of a low-class family in a disreputable part of the Empire, and had begun his career as an enlisted soldier (miles). Remarkably, Maximinus never visited Rome while Emperor. Furthermore, his reign represents one of the last sallies of the increasingly impotent Senate's attempts to control the Empire; the Senate backed two pairs of co-Emperors from its own number against Maximinus.
The accession to the purple of Marcus Antonius Gordianus retroactively created a dynasty out of the ill-fated African uprising of the Gordiani; as they did not successfully overthrow Maximinus, the preceding Gordiani are more properly regarded as failed usurperss than as Emperors, but Gordianus's accession makes the family a quasi-dynasty, which may or may not be regarded as having been restored to the purple ΰ la Severi.
Gordianan Emperors:
Gordianus I's wife Fabia Orestilla bore him two sons (Gordianus II and a son of unknown name) and a daughter (Maecia Faustina); that daughter was mother of Gordianus III, who was therefore grandson of Gordianus I and nephew of Gordianus II.
The accession to the purple of Marcus Julius Philippus "Arabicus ("the Arab") marks the second time that a praetorian prefect supplanted his Emperor (the first being Macrinus); this Syrian soldier (once erroneously thought to have been a Christian) was succeeded by the first Emperor from the Balkan Peninsula, Quintus Decius Valerinus (a noble senator of distinguished career), who was also the first Emperor to have been killed in battle with a foreign enemy (viz., the Goths). Another African, this time from Jerba off the coast of southern Tunisia donned the purple (viz. Marcus Aemilius Aemilianus).
The founder of the short-lived Valerianan dynasty, Publius Licinius Valerianus, was of a particularly distinguished patrician, Etrurian family, the Licinii. For his efforts at retrieving the badly deteriorating situation in the East, the Senate awarded him the titles Restitutor Orientis ("Restorer of the East"), Restitutor Generis Humanis ("Restorer of the Human Race") and finally Restitutor Orbis ("Restorer of the World"), but these honours fail to overcome the ignominy wherewith his reign ended: Valerianus was the first Emperor to be captured by a foreign enemy, and was used as a footstool by the Great King Shapur I of Persia, who after Valerianus's death had his skin stuffed and put on display (the only other Emperor to have been so humiliated was Rhomanos IV eight hundred years later in 1071).
Further major developments troubled the reign of P. Licinius Egnatius Gallienus: several significant rebellions arose against Gallienus's rule, including the establishment of the independent, so-called Gallic Empire (composed of Gallia, Britannia, and Hispania) in 261 by Postumus, and Gallienus erected an co-Emperor in all but name in Septimius Odenaethus, king of Palmyra (Gallienus gave Odenaethus the titles Dux Romanorum, "Leader of the Romans", and Corrector Totius Orientis, "Corrector of the Whole East").
Valerianan Emperors:
Valerianus's wife Egnatia Mariniana bore him two sons (Egnatius Gallienus and Valerianus). Gallienus himself had by his wife Julia Cornelia Salonina three sons (Valerianus, Saloninus, and Egnatius Marinianus).
The murder of Gallienus left his Dalmatian cavalry commander, Marcus Aurelius Claudius "Gothicus ("the Goth"), to don the purple. The Emperor from Illyricum recovered Hispania from the Gallic Empire, but Septimius Odenaethus's widow, Zenobia, broke with him and began to seize power in the East for herself (in 272 she began styling herself "Zenobia Augusta"). Lucius Domitius Aurelianusus built the first new wall around Rome, defeated Zenobia and recovered the lands of the Empire claimed by Palmyra, and reclaimed the remainder of the Gallic Empire; for his efforts at reunifying the Empire he was titled Restitutor Orbis ("Restorer of the World"). Aurelianus's successor Marcus Claudius Tacitus received a similar title, Restitutor Rei Publicae ("Restorer of the Republic").
The Caran dynasty was a Gallic family from Narbo on the Mediterranean coast. It was another family which came to power through treachery; Marcus Aurelius Carus, the founder of the extremely short-lived dynasty, had been his predecessor's praetorian prefect. He is particularly noted for his spectacular death: Carus is the only Emperor to have been struck by lightning.
Caran Emperors:
Carus's wife (name unknown) bore him two sons (Numerianus and Carinus) and a daughter (Aurelia Paulina).
The accession to the purple on November 20, 284, of Diocletianus, the lower-class, Greek-speaking Dalmatian commander of Carus's and Numerianus's household cavalry (protectores domestici), marked a major departure from traditional Roman constitutional theory regarding the Emperor, who was nominally first among equals; Diocletianus introduced Oriental despotism into the Imperial dignity. Whereas before Emperors had worn only a purple toga (toga purpura) and greeted with deference, Diocletianus 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.
The Tetrarchy was a system established by Diocletianus to facilitate effective government of the Empire. There were two senior emperors (augusti), one for the West and one for the East, and two junior sub-emperors (caesares), one for each senior emperor. When the senior emperors left office for whatever reason, the junior sub-emperors would become senior emperors and appoint their own junior sub-emperors; the retired senior emperors took the title senior augustus and were styled Patres Imperatorum et Caesarum ("Fathers of the Imperators and of the Caesars").
Diocletianus's wife Prisca bore him a daughter Galeria Valeria, who married Galerius (whom Diocletianus had adopted and appointed caesar on March 1, 293). Galerius's sister gave birth to a son, Maximinus Daia, and Galerius's daughter by his first wife, Valeria Maximilla, married Maxentius, son of Maximianus by his wife Eutropia; Eutropia's first marriage (to Afranius Hannibalianus) had produced a daughter, Theodora, who became the second wife of Constantius I "Chlorus" ("the Pale") in 289 (adopted by Maximianus on March 1, 293). Constantius's marriage to Theodora produced a daughter, Constantia, who married Licinius; his first marriage to St. Helena produced a son, Constantinus (see below), whose second wife was Fausta, sister of Maxentius and daughter of Maximianus.
To summarise:
The death of Galerius in May 311 and Constantinus's spectacular victory over Maxentius at the Milvian Bridge on October 28, 312, left only three Emperors: in the East, Maximinus Daia; in the West, Licinius and Constantinus. Licinius defeated Maximinus Daia in April 313 at Tarsus, and the latter committed suicide shortly thereafter, leaving Licinius and Constantinus the only Emperors; they governed the Empire along the usual lines of East and West, respectively, discarded the defunct Tetrarchical system, warred against one another in 316 317, and again in 324 325. The execution of Licinius in spring 325 left Constantinus the first sole Emperor since Diocletianus made Maximianus his co-Emperor in 286.
The Constantinian dynasty properly began with Constantius "Chlorus (caesar, 293, augustus, 305), an experienced Illyrian soldier and general; the Constantiniani were originally another family of "Barracks Emperors". The dynasty retained and reinforced the monarchical evolution of the Imperial dignity, and sponsored the pivotal Edict of Milan in 312, which extended official toleration to Christianity, which religion had suffered considerable persecution under recent Emperors. Constantinus I undertook major reforms of Imperial administration and military organisation, founded a new Imperial capital at Constantinople on November 8, 324, summoned the first Christian ecumenical council (I Nicaea, 325), and became the first Christian Emperor in 337.
Constantinian Emperors:
Julianus the Apostate famously attempted to restore paganism in the Empire, and became the second Emperor (after Decius) to die in battle with a foreign enemy (viz., the Persians).
Constantius I "Chlorus" married twice; his first wife St. Helena bore him a son, Constantinus I whose second wife Fausta (daughter of Maximianus and Eutropia; sister of Maxentius; half-sister of Constantius I's second wife Theodora) bore him three sons (Constantinus II, Constantius II, and Constans I) and two daughters (Constantia and Helena); these children were nieces and nephews of Maxentius, half-nieces and half-nephews of Licinius (who had married their father's half-sister), and grandchildren of Maximianus. Constantius I's second wife Theodora (stepdaughter of Maximianus and half-sister of Fausta) bore him two sons (Flavius Dalmatius and Iulius Constantius) and two daughters (Eutropia and Constantia, the wife of Licinius). Iulius Constantius's sons Constantius Gallus and Julianus married Constantinus I's daughters by Fausta, Constantia and Helena, respectively. Constantius II's daughter Constantia married Gratianus (see below), the son of Valentinianus I (see below).
To summarise:
Jovianus was one of Julianus the Apostate's senior generals, and was chosen as his successor by the army shortly after his death in 363; he died in February 364 without heir.
The Valentinian dynasty, yet another lower-class military family (this time of Pannonian extraction), is in a very loose sense a marital continuation of the Constantinian dynasty (Gratianus was son-in-law of Constantius II, the penultimate Constantinian Emperor). Although the dynastic founder, Valentinianus I, had made his career as a soldier and general, he was not a "Barracks Emperor"; rather, he was elevated to the purple by a conclave of senior generals and civil officials after the death of Jovianus.
Valentinian Emperors:
Valens became the third Emperor (after Decius and Julianus) to be killed in battle with a foreign enemy (viz., the Goths); only two more Emperors were ever killed in battle by foreign enemies (Nikephoros I by the Bulgars in 811 and Konstantinos XI Palaeologos by the Turks in 1453).
Valentinianus I was the elder brother of Valens, and married twice; his first wife Marina Severa bore him a son (Gratianus, whose first wife was Constantia, daughter of Constantius II), and his second wife Justina (widow of Magnentius) bore him a daughter (Galla, second wife of Theodosius I, see below) and a son ('Valentinianus II).
Arbogast, Valentinianus II's general-in-chief, murdered him in May 392, and replaced him with a puppet Emperor, Eugenius, a former rhetorician. Eugenius was overthrown two years later by Theodosius I (see below), Valentinianus II's brother-in-law.
Much as the Valentinian dynasty was loosely connected to the Constantinian dynasty by marriage, the Theodosian dynasty was loosely connected to the Valentinian; the first Theodosian Emperor, Theodosius I (historically known as "the Great") was son-in-law of Valentinianus I. Although he was a Spaniard of military background, like Valentinianus, he was no "Barracks Emperor"; he was lawfully and voluntarily elevated to the purple in the East by the reigning Emperor Gratianus, his half-brother-in-law, on January 19, 379. He abolished paganism entirely and made Christianity the official religion of the Empire in 391, overthrew Arbogast and his puppet Emperor, Eugenius, in the West in 394, and is the last Emperor to rule both East and West.
Theodosian Emperors:
Marcianus is the first Emperor to be honoured as a saint (by the Orthodox Church); his feast day (together with that of his wife, St. Pulcheria) is February 17.
By the time the Visigoths under Alaric entered Italy and sacked Rome in 410 the first time a foreign army had set foot in Rome since 390 BC, some 800 years earlier the Imperial court had long since been established at Ravenna, and Rome had ceased to be capital of the Empire either in East or West; indeed, by this point, the Bishop of Rome was one of the few senior Ecclesiastical or Imperial officials in the Empire to actually reside there.
Theodosius I married twice; first to Aelia Flacilla, who bore him two sons (Arcadius and Honorius), and second to Galla (daughter of Valentinianus I by his second wife Justina, widow of Magnentius), who bore him a daughter (Galla Placidia). Arcadius's wife Eudoxia bore him a daughter (St. Pulcheria) and a son (Theodosius II), who became Emperor at age seven. After Theodosius II's death, his sister Pulcheria married St. Marcianus, a Thracian soldier of common stock. Constantius III married Arcadius's and Honorius's sister Galla Placidia, and she bore him a son (Valentinianus III). Valentinianus III's wife Eudoxia (who after his death married Petronius Maximus, see below) bore him a son, Placidia, who married Olybrius (see below).
The wealthy senator Petronius Maximus, who succeeded Valentinianus III, had attempted to secure his position by marrying Valentinianus's widow, Eudoxia. The final collapse of the Empire in the West was marked by increasingly ineffectual puppet Emperors dominated by their Germanic masters of the soldiers. The most pointed example of this is the Suebian general Ricimer, who became a "Shadow Emperor" by deposing Avitus, installing and subsequently deposing (and murdering) Majorianus, installing (and possibly subsequently murdering) Libius Severus, ruling the Empire himself during an eighteen-month interregnum, deposing and killing Anthemius, and installing Olybrius. His position as "Shadow Emperor" was in turn held by his nephew Gundobad and Orestes; Odoacer simply overthrew Orestes's puppet Emperor, Romulus Augustus, in 476and ruled Italy as nominal subordinate of the Emperor-in-exile, Iulius Nepos, who continued to reign in Dalmatia until 480.
Both Ricimer and Olybrius (who was never acknowledged and was considered a usurper by the Eastern Emperor) died in 472, and were replaced by the Burgundian prince Gundobad and his puppet Emperor Glycerius, a former court functionary. Glycerius was deposed (but not killed) by Iulius Nepos, the candidate (and nephew-in-law) of the Eastern Emperor, who was in turn driven into exile in Dalmatia in 475 by his master of the soldiers, Orestes, who installed his own son Romulus "Augustulus" ("Little Augustus"). Orestes was killed and Romulus Augustulus deposed (but not killed) by Odoacer in 476, and Iulius Nepos continued to reign as Emperor-in-exile until his death in 480 (the Eastern Emperor did not recognise Romulus Augustulus and considered him a usurper).
''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 so-called "Holy Roman Emperors".
See also: Gallic Empire; Byzantine Empire and List of Byzantine Emperors; Holy Roman Empire and List of Holy Roman Emperors; Latin Empire of Constantinople; Julio-Claudian family tree; Severan dynasty family tree; Roman usurpers and List of Roman usurpers; victory titles and List of Imperial Victory Titles; Praetorian Prefect
Overview
Abbreviations
The Principate
Julio-Claudian Dynasty
Dynastic Relationships:Non-Dynastic
Flavian Dynasty
Dynastic Relationships:Nervan-Antonine Dynasty
Dynastic Relationships:Non-Dynastic
Commodus's murder on December 31, 192 was immediately followed the next day by the accession of Pertinax, the urban prefect (praefectus urbanus). He was murdered by the Praetorian Guard in late March 193. The consular Didius Julianus was installed by Pertinax's murderers, and was himself murdered on June 1 by a partisan of the rebellious governor of Pannonia Superior, Septimius Severus (see below).Severan Dynasty
Dynastic Relationships:Non-Dynastic
Macrinus was praetorian prefect (praefectus praetorio) under "Caracalla", whom he may have conspired to murder in April 217. His wife Nonia Celsa bore him a son, Diadumenianus, whom he made co-Emperor in 218; both were executed by partisans of "Elagabalus" (see below).Severan Dynasty (Restored)
Dynastic Relationships:The Crisis of the Third Century
Non-Dynastic
Maximinus "Thrax" was commander of new recruits on the Rhine frontier when Alexander Severus was murdered by mutineers; he was acclaimed Emperor by his troops in March 235, and in January 238 put down a rebellion by the governor of Africa Proconsularis (i.e., modern Tunisia) and his son, Gordianus I and Gordianus II; Gordianus was a consular of distinguished family and reigned 20 days with his son as co-Emperor. Immediately afterward the Senate backed a second pair of co-Emperors, the patrician consulars Pupienus and Balbinus, and Maximinus was murdered by his own troops in April that year. The senatorial co-Emperors were murdered by the Praetorian Guard a month later in May 238, having reigned 99 days.Gordianan Dynasty
Dynastic Relationships:Non-Dynastic
Philippus "Arabicus" was praetorian prefect under the late Gordianus III, whose own soldiers mutinied against him. He installed his son Marcus Julius Philippus as co-Emperor, but both were killed in 249 by partisans of Philippus's rebellious governor of Moesia and Pannonia, the consular Decius. Decius's younger son, Hostilianus, was subsequently adopted by and proclaimed co-Emperor with Trebonianus Gallus in June 251 (and promptly died of plague in July); Trebonianus Gallus replaced Decius's son with his own, Volusianus, but father and son co-Emperors were murdered in August 253 by partisans of Trebonianus Gallus's own rebellious governor of Moesia Superior, the consular Aemilianus, who was murdered by his own soldiers after a reign of 88 days.Valerianan Dynasty
Dynastic Relationships:Non-Dynastic
Claudius II "Gothicus" died of plague in August 270, and was briefly succeeded by his brother, Quintillus, who committed suicide in September and allowed the purple to pass to his own cavalry commander, Aurelianus, who was himself murdered by his Praetorian Guard (again). Tacitus was an elderly senator and probably a general brought out of retirement when it was realised that no-one stood ready to don the purple after Aurelianus's death, and was murdered after six months and succeeded for 88 days by his praetorian prefect, Florianus, who promptly became the third Emperor murdered in 276. Probus, a formidable general of unknown family from the Danube frontier, next donned the purple, only to be murdered at the instigation of his praetorian prefect, Carus (see below).Caran Dynasty
Dynastic Relationships:The Dominate
The Tetrarchy
Emperors in the East
Emperors in the West
Note: In 307, the augustus Severus was murdered by mutinous soldiers while attempting to suppress the rebellion and usurpation of Maxentius, who had invited his father Maximianus to return from retirement and reassume the purple as augustus with him. Maxentius and Maximianus reigned in the West as augusti co-operating with Constantinus as caesar until the Imperial conference at Carnutum in November 308, whereat Constantinus confirmed as caesar, Maximianus deposed, and Licinius appointed augustus in his place. Maxentius continued to hold power as a rival Emperor until 312; his father Maximianus (the first Emperor to be restored) committed suicide after an attempt to don the purple a third time in 310.Tetrarchical Relationships
End of the Tetrarchy
Emperor in the East
Emperor in the West
Constantinian Dynasty
Before Constantinus's death, he divided the Empire into four parts governed by caesares, apparently intending to re-establish the Tetrarchy. He left most of the West to his son Constantinus II, the East to his son Constantius II, Italia and the Upper Danube to his son Constans I, and Greece and the Lower Danube to his half-nephew Flavius Dalmatius. Dalmatius was killed shortly after Constantinus's death, and the Empire was divided into three parts.Emperor in Britannia, Hispania, and Gallia
In 340, Constantinus II invaded Constans I's territory in Italia; he was defeated and killed at Aquileia, and his provinces passed to the control of the brother whom he had attempted to displace.Emperor in Italia and Africa
In 340, Constans I annexed the provinces of his late brother Constantinus II, and became Emperor of the whole West.Emperors in the West
Magnentius's defeat in 353 by Constantius II, the last of the brother Emperors, reunified the Empire under a single Emperor. Emperor in the East
In 353, Constantius II defeated the usurper Magnentius at Lyons and became sole Emperor.Emperors
Dynastic Relationships
Non-Dynastic
Valentinianan Dynasty
Emperors in the West
Emperor in the East
Dynastic Relationships
Non-Dynastic
The West
Theodosian Dynasty
After Theodosius's death in 395, the Empire was permanently divided into East and West by his seventeen-year-old and ten-year-old sons, Arcadius and Honorius, respectively. Emperors in the East
Emperors in the West
Dynastic Relationships
The Empire in the West
Non-Dynastic
Petronius Maximus he was killed trying to flee Rome presently under imminent threat of attack by the Vandals eleven weeks after donning the purple. He was succeeded by his master of the soldiers, Avitus, who was acclaimed at Tolosa with the backing of the Visigothic king, Theodoric II. He was in turn overthrown (but not killed) by his own master of the soldiers, Ricimer, who was responsible for both the installation and removal of Majorianus and of Libius Severus, the removal of Anthemius (installed as the Eastern Emperor's candidate), and the installation of Olybrius husband of Valentinianus III's daughter (and Petronius Maximus's step-daughter) Placidia, and loosely a member of the Theodosian dynasty. The Empire in the East
Leonine Dynasty
For Roman emperors in the East after Zeno, see list of so-called "Byzantine Emperors".