In fact, the word Emperor is a corruption of the Latin Imperator which implies a military commander rather than a civil monarch.

Augustus was proclaimed Imperator, Gaius Julius never was.

In fact, the most widely admitted date for the end of the western roman empire is 476, when Romulus Augustulus was deposed by the barbaric mercenay Odoacer.

All the other "emperors" are, as you can guess from their names, Germanic leaders (simple soldiers like Odoacer, or magnificient kings such as the Ostrogoth Theodoric the Great). They tried to preserve an imperial power in Rome, but they failed. The first real western emperor after Augustulus was the Frank king Charlemagne (official coronation by the Pope in 800 A.D.), who unified all of western Europe under his rule, thereby laying the foundation for virtually all of European history to date.

Note 1 : The german word "Kaiser" also comes from "Caesar".
Note 2 : All of this applies only to the western empire. The Byzantine Empire (395) managed to survive until Constantinople was taken by the Turks in 1453.
There is good reason to regard Julius Caesar as the first emperor, and he was so called throughout the Middle Ages, but the convention these days is that we start with Augustus as the first. With his reign the empire became continuous. See Princeps by Gone Jackal (and to a lesser extent my Roman Empire) for a more detailed discussion of the comparative powers and titles of Caesar and Augustus.

The names Caesar and Augustus, and the military title Imperator, all continued as part of the regnal titles of the emperors. (In the later period of the Tetrarchy the Caesar was deputy emperor to the Augustus.) Their full names and styles were often very complex; the names given here are the more familiar ones.

Where multiple emperors are given at the same time, there are three possible causes: (i) they were killed or overthrown in quick succession (e.g. the year 69); (ii) the emperor shared power with his son or other intended successor; or (iii) they were rivals appointed by troops in different parts of the empire. I have made some explanatory notes where I can work out what happened.

  1. Augustus 27 BCE - 14 CE
  2. Tiberius 14-37
  3. Caligula 37-41
  4. Claudius 41-54
  5. Nero 54-68
  6. Galba 68-69
  7. Otho 69
  8. Vitellius 69
  9. Vespasian 69-79
    The year 69 is known as the year of four emperors.
  10. Titus 79-81
  11. Domitian 81-96
  12. Nerva 96-98
  13. Trajan 98-117
  14. Hadrian 117-138
  15. Antoninus Pius 138-161
  16. Marcus Aurelius and his brother Lucius Verus 161-169
  17. Marcus Aurelius alone 169-177
  18. Marcus Aurelius and his son Commodus 177-180
  19. Commodus alone 180-192
  20. Pertinax 193
  21. Didius Julianus 193
  22. Septimius Severus 193-198
  23. Septimius Severus and his son Geta 198-209
  24. Septimius Severus and his sons Geta and Caracalla 209-211
  25. Geta alone 211
  26. Caracalla alone 211-217
  27. Macrinus 217-218
  28. Macrinus and his son Diadumenian 218
  29. Elagabalus (or Heliogabalus) 218-222
  30. Severus Alexander 222-235
  31. Maximinius the Thracian 235-238
  32. Gordian I and his son Gordian II 238
  33. Balbinus and Pupienus Maximus 238
  34. Gordian III 238-244
  35. Philip the Arabian 244-247
  36. Philip the Arabian and his son Philip II 247-249
  37. Decius 249-251
  38. Decius and his son Herennius Etruscus 251
  39. Hostilian and Trebonianus Gallus 251
  40. Trebonianus Gallus and his son Velusian 251-253
  41. Aemilian 253
  42. Valerian and his son Gallienus 253-260
    Valerian was one of the very few who was still alive after the end of his reign.
  43. Gallienus and his son Saloninus 260
  44. Gallienus alone 260-268
  45. Claudius II 268-270
  46. Quintillus 270
  47. Aurelian 270-275
  48. Tacitus 275-276
  49. Florian 276
  50. Probus 276-282
  51. Carus 282-283
  52. Numerian and his brother Carinus 283-284
  53. Carinus and Diocletian 284-285
  54. Diocletian alone 285-286
  55. Diocletian and Maximian 286-305
    Uh oh, now it gets complicated. This was the Tetrarchy with two Augusti as main emperors, east and west, and two Caesares as deputies. I've drawn myself some time-lines to try to work out which reigns overlapped. I am listing only the emperors and co-regents, not their deputies. Maximian, having abdicated with Diocletian in 305, actually resumed the title of Augustus in 307-308 and in 309-310, but if I try to fit him in down here you'll reach out of the chatterbox and throttle me till my eyes bug out, so let's not.
  56. Galerius and Constantius Chlorus 305-306
  57. Galerius and Severus 306-307
  58. Galerius and Maxentius and Constantine the Great 307-308
  59. Galerius and Maxentius and Constantine the Great and Licinius 308-310
  60. Galerius and Maxentius and Constantine the Great and Licinius and Maximinus II 310-311
    I'm not making this up, you know.
  61. Maxentius and Constantine the Great and Licinius and Maximinus II 311-312
  62. Constantine the Great and Licinius and Maximinus II 312-313
  63. Constantine the Great and Licinius 313-316
  64. Constantine the Great and Licinius and Valerius Valens 316-317
  65. Constantine the Great and Licinius 317-324
  66. Constantine the Great and Martinian 324
  67. Constantine the Great alone 324-337
  68. Constantine II and Constans and Constantius II, brothers, 337-340
  69. Constans and Constantius II 340-350
  70. Constantius II and Magnentius 350-353
  71. Constantius II alone 353-360
  72. Constantius II and Julian the Apostate 360-361
  73. Julian the Apostate alone 361-363
  74. Jovian 363-364
  75. Valentinian I and his brother Valens 364-367
  76. Valentinian I and Valens and Gratian 367-375
  77. Valens and Gratian and Valentinian II 375-378
  78. Gratian and Valentinian II 378-379
  79. Gratian and Valentinian II and Theodosius the Great 379-383
  80. Valentinian II and Theodosius the Great and Maximus and Arcadius 383-387
  81. Valentinian II and Theodosius the Great and Maximus and Arcadius and Victor 387-388
  82. Valentinian II and Theodosius the Great and Arcadius 388-392
  83. Theodosius the Great and Arcadius and Eugenius 392-393
  84. Theodosius the Great and Arcadius and Eugenius and Honorius 393-394
  85. Theodosius the Great and Arcadius and Honorius 394-395
    footnote 17
On the death of Theodosius the empire was permanently divided into independent states, the Western Roman Empire going to his son Honorius, and Eastern Roman Empire, better known as The Byzantine Empire, going to his son Arcadius. See under those two nodes for subsequent emperors.

Right, the above list is so confusing that here it is again in a more familiar form, one line per emperor; this means there's lots of overlapping dates. Refer to the above to resolve them; refer to this one below if you just want a simple list. (In case I made a mistake rearranging it, the one above is more accurate.)

  1. Augustus 27 BCE - 14 CE
  2. Tiberius 14-37
  3. Caligula 37-41
  4. Claudius 41-54
  5. Nero 54-68
  6. Galba 68-69
  7. Otho 69
  8. Vitellius 69
  9. Vespasian 69-79
  10. Titus 79-81
  11. Domitian 81-96
  12. Nerva 96-98
  13. Trajan 98-117
  14. Hadrian 117-138
  15. Antoninus Pius 138-161
  16. Marcus Aurelius 161-180
  17. Lucius Verus 161-169
  18. Commodus 177-192
  19. Pertinax 193
  20. Didius Julianus 193
  21. Septimius Severus 193-211
  22. Geta 198-211
  23. Caracalla 209-217
  24. Macrinus 217-218
  25. Diadumenian 218
  26. Elagabalus 218-222
  27. Severus Alexander 222-235
  28. Maximinius the Thracian 235-238
  29. Gordian I 238
  30. Gordian II 238
  31. Balbinus 238
  32. Pupienus Maximus 238
  33. Gordian III 238-244
  34. Philip the Arabian 244-249
  35. Philip II 247-249
  36. Decius 249-251
  37. Herennius Etruscus 251
  38. Hostilian 251
  39. Trebonianus Gallus 251-253
  40. Velusian 251-253
  41. Aemilian 253
  42. Valerian 253-260
  43. Gallienus 253-268
  44. Saloninus 260
  45. Claudius II 268-270
  46. Quintillus 270
  47. Aurelian 270-275
  48. Tacitus 275-276
  49. Florian 276
  50. Probus 276-282
  51. Carus 282-283
  52. Numerian 283-284
  53. Carinus 283-285
  54. Diocletian 284-305
  55. Maximian 286-305
  56. Galerius 305-311
  57. Constantius Chlorus 305-306
  58. Severus 306-307
  59. Maxentius 307-312
  60. Constantine the Great 307-337
  61. Licinius 308-324
  62. Maximinus II 310-313
  63. Valerius Valens 316-317
  64. Martinian 324
  65. Constantine II 337-340
  66. Constans 337-350
  67. Constantius II 337-361
  68. Magnentius 350-353
  69. Julian the Apostate 360-363
  70. Jovian 363-364
  71. Valentinian I 364-375
  72. Valens 364-378
  73. Gratian 367-383
  74. Valentinian II 375-392
  75. Theodosius the Great 379-395
  76. Maximus 383-388
  77. Arcadius 383-395
  78. Victor 387-388
  79. Eugenius 392-394
  80. Honorius 393-395

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