The Antonine Dynasty (96–192 AD) — Nerva, Trajan, Hadrian, Antoninus Pius, Marcus Aurelius — is often called the period of the 'Five Good Emperors,' a label coined by Machiavelli and popularized by Gibbon, who wrote that this was the period 'in the history of the world during which the condition of the human race was most happy and prosperous.'

The dynasty's coherence came partly from the practice of adoptive succession: each emperor adopted his successor rather than transmitting power to a biological son. This was either a principled constitutional innovation or a pragmatic adaptation to circumstances (most emperors in this dynasty had no surviving sons), but its practical effect was that each emperor could choose his successor on merit — which happened to produce a succession of generally capable rulers.

Trajan (98–117 AD) expanded the empire to its maximum extent with the conquest of Dacia (roughly modern Romania) and temporary conquest of Mesopotamia. The Dacian Wars are documented in extraordinary visual detail on Trajan's Column in Rome, which spirals upward with scenes of military operations that are primary evidence for Roman military technology, tactics, and equipment. The Dacian gold and silver that came to Rome with the conquest funded Trajan's extensive building program.

Marcus Aurelius (161–180 AD) combined effective military command — he spent much of his reign on the Danube frontier defending against Germanic incursions — with Stoic philosophical writing in his private journal (the Meditations). The text, never intended for publication, documents a man genuinely trying to live by Stoic principles in circumstances that repeatedly tested those principles. It is both the most influential Stoic text and one of the more intimate personal documents that survives from antiquity.