| Ruler | Date |
| Pompey | 63 BC |
| Julius Caesar | 47-44 BC |
| Augustus Caesar | 27 BC-AD 14 |
| Tiberius Caesar | 14-37 |
| Caligula Caesar | 37-41 |
| Claudius Caesar | 41-54 |
| Nero Caesar | 54-68 |
| Galba | 68-69 |
| Otho | 69 |
| Vitellius | 69 |
| Vespasian | 69-79 |
| Titus | 79-81 |
| Domitian | 81-96 |
| Nerva | 96-98 |
| Trajan | 98-117 |
| Hadrian | 117-138 |
| Antonius Pius | 138-161 |
| Marcus Aurelius | 161-180 |
| Lucius Aurelius Verus | 161-169 |
| Commodus | 180-192 |
| Pertinax | 193 |
| Didius Julian | 193 |
| Septimius Severus | 193-211 |
| Caracalla | 211-217 |
| Geta | 211-212 |
| Macrinus | 217-218 |
| Heliogabalus | 218-222 |
| Alexander Severus | 222-235 |
| Maximinus Thrax | 235-238 |
| Gordian I | 238 |
| Gordian II | 238 |
| Balbinus | 238 |
| Pupienus | 238 |
| Gordian III | 238-244 |
| Philip | 244-249 |
| Decius | 249-251 |
| Gallus | 251-253 |
| Hostilian | 251 |
| Aemilianus | 253 |
| Valerian | 253-260 |
| Gallienus | 253-268 |
| Claudius II | 268-270 |
| Aurelian | 270-275 |
| Tacitus | 275-276 |
| Florian | 276 |
| Probus | 276-282 |
| Carus | 282-283 |
| Carinus | 283-285 |
| Numerianus | 283-284 |
| Diocletian | 284-305 |
| Maximian | 286-305 |
| Constantius | 305-306 |
| Galerius | 305-311 |
| Constantine I | 306-337 |
| Maximian | 306-308 |
| Maxentius | 306-312 |
| Severus | 306-307 |
| Licinius | 308-324 |
| Maximinus | 308-313 |
| Constantius II | 337-361 |
| Constans | 337-350 |
| Constantine II | 337-340 |
| Magnentius | 350-353 |
| Julian | 361-363 |
| Jovian | 363-364 |
| Valentinian (West) | 364-375 |
| Valens (East) | 364-368 |
| Gratian (West) | 367-383 |
| Valentinian II (West) | 375-392 |
| Theodosius I | 379-395 |
| Maximus (West) | 383-388 |
| Eugenius (West) | 392-394 |
| Emperors in the West | |
| Honorius | 395-423 |
| Constantius III | 421 |
| Valentinian III | 425-455 |
| Petronius Maximus | 455 |
| Avitus | 455-456 |
| Majorian | 457-461 |
| Libius Severus | 461-465 |
| Anthemius | 467-472 |
| Olybrius | 472 |
| Glycerius | 473 |
| Julius Nepos | 473-475 |
| Romulus Augustulus | 475-476 |
| Emperors in the East | |
| Arcadius | 395-408 |
| Theodosius II | 408-450 |
| Marcian | 450-457 |
| Leo I | 457-474 |
| Leo II | 473-474 |
| Zeno | 474-491 |
*At various times, but especially after 283, the Roman imperial title was shared by two or more rulers. In 395 the empire was divided permanently into eastern and western portions. The year 476 marks the traditional end of the empire in the West; the empire in the East (the Byzantine Empire) continued to exist for nearly 1,000 years.