Pretenders and usurpers in italics
| Rule | Emperor | Reigned approx. | Death | Origin | Notes |
| 31BC-14 | Caesar divi filius Augustus (Gaius Octavianus) | Natural causes | Italia | Father of the Principate. | |
| 14-37 | Tiberius Claudius Nero | Natural causes | Italia | Adopted heir. | |
| 37-41 | Gaius "Caligula" Caesar | Assasinated | Italia (Antium) | Adopted heir. | |
| 41-54 | Claudius Nero Germanicus | Food poisoning | Italia / Lugdunum | Praetorian coup, uncle of Gaius. | |
| 54-68 68 68 |
Nero Claudius Caesar pretender: C. Iulius Vindex pretender: L. Clodius Macer |
Suicide | Italia | Adopted heir, son of Claudius' wife Agrippina. | |
| 68-69 | Servius Sulpicius Galba | Executed | Italia | Revolted against Nero. | |
| 69 | Marcus Salvius Otho | Suicide | Italia (Ferentium) | Pretorian coup, Etruscan. | |
| 69 | Aulus Vitellius Germanicus | Executed | Italia | Elected by army. | |
| 69-79 | Titus Flavius Vespasianus | Natural causes | Italia (Falacrinae) | Military coup. | |
| 79-81 | Titus Flavius Vespasianus | Natural causes (malaria) | Italia | Son of Vespasianus. | |
| 81-96 89 |
Titus Flavius Domitianus usurper: L. Antonius Saturninus |
Assasinated | Italia | Son of Vespasianus. | |
| 96-98 | Marcus Cocceius Nerva | Natural causes (apoplexy) | Italia / Umbria (Narnia) | Elected by Senate. | |
| 98-117 | Marcus Ulpius Traianus | Natural causes | Baetica (Italica) | Adopted. | |
| 117-138 | Publius Aelius Hadrianus | Natural causes | Baetica (Italica) | Adopted. | |
| 138-161 | Titus Aurelius Antoninus "Pius" | Natural causes | Italia (Lanuvium) | Adopted. | |
| 161-180 161-166 175 |
Marcus Aurelius Antoninus Lucius Aurelius Verus usurper: Avidius Cassus |
Natural causes | Italia (Roma) | Adopted. | |
| 180-192 | Lucius Aurelius Commodus Antoninus | 15 years | Assasinated | Italia (Roma) | Son of M. Aurelius. |
| 192-193 | Publius Helvetius Pertinax | 2 months | Assasinated | Italia (Alba Pompeia) | Praetorian coup. |
| 193 | Marcus Didius Severus Iulianus | 2 months | Assasinated | Italia (Mediolanum) | Bought the Empire from Praetorians. |
| 193-211 193-194 193-197 |
Lucius Septimius Severus usurper: Lucius Pescennius Niger usurper: Didius Clodius Septimus Albinus |
17 years 2 months | Natural causes Killed in battle Killed in battle |
Africa (Leptis Magna) | Start of military dictatorship. |
| 211-217 211 |
M. A. Antoninus "Caracalla" (Septimus Bassianus) Publius Septimius Geta |
19 years 2 years 3 months |
Assasinated Assasinated |
Punic-syrian (Lugdunum) | Sons of Severus. |
| 217-218 | Marcus Opellius Severus Macrinus (with son Diadumenianus) |
1 year 2 months | Assasinated | Mauretania (Caesarea) | Preatorian coup. |
| 218-222 | M. A. Antoninus "Elagabalus" (Varius Avitius) usurper: Seleucus usurper: Uranius Antoninus usurper: Gellius Maximus usurper: Verus |
3 years 9 months | Assasinated |
Syria (Emesa) | Puppet emperor; state ruled by his mother Julia Bassiana and grandmother Julia Maesa. |
| 222-235 | Severus Alexander (Bassianus Alexianus) usurper: Taurinus |
13 years | Assasinated Accident |
Syria (Arca Caesarea) | Puppet emperor; regent Julia Mamaea. |
| 235-238 | Iulius Verus Maximinus I "Thrax" usurpers: Magnus and Alexander |
3 years 3 months | Assasinated | Moesia | Military coup, state in anarchy. |
| 238 238 |
Marcus Antonius Gordianus I Sempronianus Marcus Antonius Gordianus II Sempronianus |
3 weeks 3 weeks |
Suicide Killed in battle |
Asia (Gordion) Africa (Carthago) |
Tax revolt in Africa, Civil war. |
| 238 238 |
Marcus Clodius Pupienus Maximus Decimus Caelius Calvinus Balbinus |
3 months 3 months |
Executed Executed |
Italia Italia |
Elected by Senate, civil war. |
| 238-244 240 |
Marcus Antonius Gordianus III pretender: Sabinianus |
Assasinated | Africa (Carthago) Africa (Carthago) |
Puppet emperor, praetorian rule. | |
| 244-249 247-249 248 |
Marcus Iulius Filippus I "Arabs" (with son Filippus II) usurpers: Pacatianus and Iotapianus |
5 years 6 months | Killed in battle | Arabia | Military coup. |
| 249-251 251 250 250 |
Gaius Messius Quintus Traianus Decius (with sons Herennius Etruscus and Hostilius) usurper: Titus Iulius Priscus usurper: Iulius Valens Licinianus |
1 year 9 months | Killed in battle | Pannonia (Budalia) | Military coup by Pannonian legions. Made sacrifice to State Gods compulsory. |
| 251-3 253 253 |
Gaius Vibius Trebonianus Gallus (with son C. V. Volusianus) pretender: Uranius Antoninus |
2 years | Assasinated Assasinated |
Italia (Perusia) |
From old etruscan family. Eastern empire revolted under priests of Baal. |
| 253 | Marcus Aemilius Aemilianus | 3 months | Assasinated | Africa (Girba) | Military coup. |
| 253-260 253-268 260 260-261 261 261-262 |
Publius Licinius Cornelius Valerianus Publius Licinius Egnatius Gallienus usurper: Ingenuus, Regalianus usurpers: Macrianus, Quietus usurpers: Valens, Piso, Ballista usurpers: Mussius Aemilianus, Memor |
6 years 15 years |
Captured in battle (Persians) Assasinated (conspiracy of praetorians, Claudius and Aurelianus) |
Illyria? Illyria? |
Elected by army. |
| Son of Valerianus. After Valerian's death, the empire dissolves. | |||||
260-269 269 269 269-271 271-274 273-274 274 |
GALLIC EMPIRE Marcus Cassianius Latinius Postumus usurper: Laelianus Marcus Aurelius Marius Marcus Piavonius Victorinus Caius Pius Esuvius Tetricus I (with son Tetricus II) usurper: Faustinus |
9 years 8 months 2 weeks 2 years 3 years |
Assasinated Assasinated Assasinated Natural causes Natural causes |
Gallic Empire forms a breakaway state. | |
260-267 270-272 |
PALMYRENE EMPIRE Odenathus (Odainath) Zenobia (with son Septimius Wahballath) |
3 years |
Assasinated Natural causes |
Palmyra Palmyra |
Secessionist state |
268-270 270 |
CENTRAL EMPIRE Marcus Aurelius Claudius II "Gothicus" Marcus Aurelius Claudius Quintillus |
1 year 5 months 3 months |
Natural causes (plague) Suicide |
Illyria Illyria |
Military coup. |
| 270-275 271-271 275 |
Lucius Domitius Aurelianus usurpers: Domitianus, Urbanus, Septimius regent: Ulpia Severina |
5 years 3 months |
Assasinated | Dacia | Sol Invictus (Mithras) as state religion. Empress Ulpia Severina ruled after Aurelian's death. |
| 275-276 | Marcus Claudius Tacitus | 7 months | Assasinated | Italia (Baiae) | Elected by Senate. |
| 276 | Marcus Annius Florianus | 2 months | Assasinated | Italia | Half-brother of Tacitus. |
| 276-282 280 280-281 |
Marcus Aurelius Probus usurper: Saturninus usurpers: Proculus and Bonosus |
6 years | Assasinated | Illyria (Sirmium) | Military coup. |
| 282-283 283-284 283-285 |
Marcus Aurelius Carus Marcus Aurelius Numerianus Marcis Aurelius Carinus |
10 months 1 year 2 months 1 year 8 months |
Natural causes? Assasinated Assasinated |
Narbonensis (Narbo) | Praetorian coup. |
284-305 286-305 297 |
TETRARCHY Gaius Valerius Diocletianus Iovius (Diocles) Aurelius Valerius Maximianus Herculius usurper: L. Domitius Domitianus |
20 years 5 months 19 years 1 months |
Natual causes Suicide |
Dalmatia Illyria (Sirmium) Egypt |
Revision of the army and provincial system. Bagaudae revolt in Gallia (led by Amandus), donatist uprising in Africa. |
286-293 293-297 |
BRITISH EMPIRE Mausaeus Carausius Allectus |
Assasinated Killed in battle |
Belgica (Menapi) |
Britain and Bononia revolted. |
|
305-306 306-307 |
WESTERN EMPIRE Flavius Valerius Constantius I "Chlorus" Flavius Valerius Severus II |
1 year 2 months 8 months |
Natural causes Executed |
Moesia (Naissos) |
Invaded Britain and crushed the secessionists. |
| 306-312 308-309 |
M. Aurelius Valerius Maxentius usurper: Lucius Domitius Alexander |
6 years | Killed in battle | Italia (Praeneste) Africa |
Pretorian coup in Rome. Maxentius lost to Constantine at Saxa Rubra (28.10.312) |
305-311 310-313 |
EASTERN EMPIRE Gaius Galerius Valerius Maximianus Maximinus II Daia |
6 years 4 years 9 months |
Natural causes Natural causes |
Dacia (Serdica) |
Persecutions of christians. |
| 308-324 | Valerius Licinianus Licinius (with Martianus) |
16 years | Executed Executed |
Dacia | Christians purged from the army. |
| 307-337 | Flavius Valerius Constantinus I | 30 years | Natural causes | Moesia (Naissos) | Military coup. Patron of christianity, deprived pagan cults of their wealth. Christus as state religion in 324. |
| 337-340 337-350 350-353 337-361 350 355 |
Flavius Claudius Constantinus II Flavius Iulius Constans I usurper: Flavius Magnus Magnentius Flavius Iulius Constantius II usurpers: Nepotianus and Vetranio usurper: Silvanus |
2 years 6 months 12 years 6 months 24 years 1 month |
Killed in battle Assasinated Suicide Natural causes |
Gallia (Arelate) Britannia |
Realm divided between Constantine's three quarreling sons. |
| 360-363 | Flavius Claudius Julianus | 3 years 3 months | Assasinated | Pagan revival. | |
| 363-364 | Flavius Jovianus | 7 months | Accidental | Persecution of pagans and burning of libraries. Non-christians purged from the army. | |
| 364-375 364-378 |
Flavius Valentinianus I Flavius Valens |
11 years 8 months | Natural causes | Illyria (Cibalae) Illyria (Cibalae) |
Severe persecutions against philosophers. |
| 367-383 | Flavius Gratianus | 16 years | Assasinated | Illyria (Sirmium) | Gave up the title of Pontifex Maximus. |
| 375-392 383-388 |
Flavius Valentinianus II usurper: Magnus Maximus |
16 years | Assasinated |
Pannonia (Aquincum) Hispania |
Child-emperor. |
| 379-395 392-394 |
Flavius Theodosius I usurper: Arbogast (with Flavius Eugenius) |
16 years | Natural causes | Hispania (Cauca) |
All other religions (except judaism) made illegal. Persecutions of heretics, disagreement with Church dogma outlawed. |