Pax Romana was the long period of relative peace and minimal expansion by military force experienced by the Roman Empire

Roman Empire

The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

 in the 1st and 2nd centuries AD. Since it was established by Caesar Augustus it is sometimes called Pax Augusta. Its span was about 207 years (27 BC to 180 AD).
The Pax Romana, or Roman Peace, is a Latin term referring to the Empire in its glorified prime. From the end of the Republican civil wars, beginning with the accession of Augustus in 27 BC, this era in Roman history lasted until 180 AD and the death of Marcus Aurelius.