The Roman–Persian Wars were a series of conflicts between states of the Greco-Roman world and two successive Iranic empires: the Parthian and the Sassanid. Battles between the Parthian Empire and the Roman Republic began in 92 BC; wars began under the late Republic, and continued through the Roman and Sassanid empires. They were ended by the Arab Muslim invasions, which struck the Sassanid and Byzantine East Roman empires with shattering effect shortly after the end of the last war between them.

Although warfare between the Romans and the Parthians/Sassanids lasted for seven centuries, the frontier remained largely stable. A game of tug of war ensued: towns, fortifications, and provinces were continuously sacked, captured, destroyed, and traded. Neither side had the logistical strength or manpower to maintain such lengthy campaigns far from their borders, and thus neither could advance too far without risking stretching their frontiers too thin. Both sides did make conquests beyond the border, but the balance was almost always restored in time. The line of stalemate shifted in the 2nd century AD: it had run along the northern Euphrates; the new line ran east, or later northeast, across Mesopotamia to the northern Tigris. There were also several substantial shifts further north, in Armenia and the Caucasus.

The Greco-Persian Wars (also often called the Persian Wars) were a series of conflicts between the Achaemenid Empire of Persia and city-states of the Hellenic world that started in 499 BC and lasted until 449 BC. The collision between the fractious political world of the Greeks and the enormous empire of the Persians began when Cyrus the Great conquered Ionia in 547 BC. By Greek accounts, enmity between Greek and Persia continued for more than two centuries, culminating in the dissolution of the Persian Empire by Alexander the Great; the principal events of the wars, however, unfolded during the two failed Persian expeditions against Greece, in 490 and in 480/479 BC.

The Greeks themselves referred to those wars as the "Median affair" (Μηδικά, Mĕdiká). Although they were perfectly aware that the Achaemenid Empire, their enemy, was ruled by a Persian dynasty, they retained for this empire the name under which they had known it first, that of the Medes.

In 499 BC, the then tyrant of Miletus, Aristagoras, embarked on an expedition to conquer the island of Naxos, with Persian support; however, the expedition was a debacle and, pre-empting his dismissal, Aristagoras incited all of Hellenic Asia Minor into rebellion against the Persians. This was the beginning of the Ionian Revolt, which would last until 493 BC, progressively drawing more regions of Asia Minor into the conflict. Aristagoras secured military support from Athens and Eretria, and in 498 BC these forces helped capture and burn the Persian regional capital of Sardis. The Persian king Darius the Great vowed to have revenge on Athens and Eretria for this act. The revolt continued, with the two sides effectively stalemated throughout 497–495 BC. In 494 BC, the Persians regrouped, and attacked the epicentre of the revolt in Miletus. At the Battle of Lade, the Ionians suffered a decisive defeat, and the rebellion collapsed, its last embers being stamped out the following year.