(AD 14–68), the four successors of Augustus, the first Roman emperor: Tiberius (reigned 14–37), Caligula (37–41), Claudius I (41–54), and Nero (54–68). It was not a direct bloodline. Augustus had been the great-nephew and adopted son of Julius Caesar (of the Julia gens), whereas Tiberius, the adopted son of Augustus, came from the aristocratic Claudia gens. Caligula was a great-grandson of Augustus; Claudius was a nephew of Tiberius; (Tiberius) and Nero was the great-nephew and adopted son of Claudius.

The ablest of the line was Tiberius. He was undoubtedly a capable and vigorous ruler, who enforced justice in the government of the provinces, maintained the integrity of the frontiers, and husbanded the finances of the empire; but he became intensely unpopular in Roman society and in his last years became a cruel tyrant. His successor, Gaius, generally known as Caligula, became known for his wild caprices and uncontrolled passions, which issued in manifest insanity. Upon his assassination he was followed by his uncle, Claudius, whose personal disabilities made him an object of derision to his contemporaries but who had many statesmanlike faculties. His reign left an abiding mark on the history of the empire, for he carried forward its development on the lines intended by Augustus. Client-states were absorbed, southern Britain was conquered, the Romanization of the West received a powerful impulse, public works were executed in Rome and Italy, and the organization of the imperial bureaucracy made rapid strides. Nero, the last of the Julio-Claudian line, has been handed down to posterity as the incarnation of monstrous vice and fantastic luxury. But his wild excesses scarcely affected the prosperity of the empire at large; the provinces were well governed, and the war with Parthia led to a compromise in the matter of Armenia, which secured peace for half a century. The dynasty ended amid rebellion and civil war. Nero died, probably by suicide, and was succeeded by the general Galba, who had been a leader of one of the revolts.