Achaia[1][2] (Ancient Greek: Ἀχαΐα), sometimes spelled Achaea,[3][4] was a province of the Roman Empire, consisting of the Peloponnese, Attica, Boeotia, Euboea, the Cyclades and parts of Phthiotis, Aetolia and Phocis.

In 150–148 BC the Romans fought the Fourth Macedonian War, after which they annexed Macedon, formerly the largest and most powerful state in mainland Greece.

The contemporary historian Polybius blames the demagogues of the cities of the Achaean League for encouraging a rash decision and inciting a suicidal war.

At the request of the Dymaean town councillors, Quintus Fabius Maximus[a] issued a ruling, sentencing the revolutionaries to death.

[12] In the following decades, many Greek communities sought to establish treaty relationships of "friendship and alliance" with Rome, apparently finding this preferable to free status.

In 89 BC, Mithradates VI Eupator, king of Pontus, seized the Roman Province of Asia (in western Anatolia).

[14][15] As the part of the Roman East closest to Italy, Greece was a central theatre of the civil wars of the Late Republic.

Caesar's assassins, led by Marcus Junius Brutus and Gaius Cassius Longinus, based themselves in Greece during the Liberators' civil war, until their defeat by Octavian and Mark Antony of the Second Triumvirate at the Battle of Philippi in 42 BC.

After the defeat of Antony and Cleopatra at the Battle of Actium, the Emperor Augustus separated Greece, Thessaly, and part of Epirus from Macedonia in 27 BC.

[18][16] The Roman Emperor Nero visited Greece in AD 66, and performed at the Ancient Olympic Games, despite the rules against non-Greek participation.

During the Marcomannic Wars, in 170 or 171, the Costoboci invaded Roman territory, sweeping south through the Balkans to Achaia, where they sacked the sanctuary of Demeter and Persephone at Eleusis.

Roman culture was highly influenced by the Greeks; as Horace said, Graecia capta ferum victorem cepit ("Captive Greece captured her rude conqueror").

The apostle Paul of Tarsus preached in Philippi, Corinth and Athens, and Greece soon became one of the most highly Christianized areas of the empire.

They then moved north and sacked Athens, before being defeated by a local force led by the Athenian Dexippus, whose writings were a source for later historians.

[26] In the aftermath of this invasion, much of the classical and imperial monuments of Athens were spoliated to build the Post-Herulian wall, which enclosed only a small area around the Acropolis.

Older scenarios of poverty, depopulation, barbarian destruction, and civil decay have been revised in light of recent archaeological discoveries.

Contemporary texts such as Hierokles' Syndekmos affirm that late antiquity Greece was highly urbanised and contained approximately eighty cities.

[28] This view of extreme prosperity is widely accepted today, and it is assumed between the 4th and 7th centuries AD, Greece may have been one of the most economically active regions in the eastern Mediterranean.