Arcadia (Greek: Ἀρκαδία) was a region in the central Peloponnese. It took its name from the mythological character Arcas and in Greek mythology, it was the home of the god Pan. In European Renaissance arts, Arcadia was celebrated as an unspoiled, harmonious wilderness; as such, it was referenced in popular culture.

There is also a modern regional unit of Greece of the same name, which is more extensive than the ancient region.

Arcadia was gradually linked in a loose confederation that included all the Arcadian towns and was named League of the Arcadians. It successfully faced in 7th century BC the threat of Sparta and the Arcadians managed to maintain their independence. They participated in the Persian Wars alongside other Greeks by sending forces to Thermopylae and Plataea. During the Peloponnesian War Arcadia allied with Sparta and Corinth. In the following years, during the period of the Hegemony of Thebes, the Theban general Epaminondas reinforced the Arcadian federation in order to form a rival pole to the neighboring Sparta. Then he founded Megalopolis, which became its new capital. Over the next centuries Arcadia weakened. It initially was subjugated by the Macedonians and later the Arcadians joined the Achaean League.

Geographically, ancient Arcadia occupied the highlands at the centre of the Peloponnese. To the north, it bordered Achaea along the ridge of high ground running from Mount Erymanthos to Mount Cyllene; most of Mount Aroania lay within Arcadia. To the east, it had borders with Argolis and Corinthia along the ridge of high ground running from Mount Cyllene round to Mount Oligyrtus and then south Mount Parthenius. To the south, the border Laconia and Messenia ran through the foothills of the Parnon and Taygetos mountain ranges, such that Arcadia contained all the headwaters of the Alpheios river, but none of the Eurotas river. To the south-west, the border with Messania ran along the tops of Mount Nomia, and Mount Elaeum, and from there the border with Elis ran along the valleys of the Erymanthos and Diagon rivers. Most of the region of Arcardia was mountainous, apart from the plains around Tegea and Megalopolis, and the valleys of the Alpheios and Ladon rivers.

The Arcadians were an ancient Greek tribe which was situated in the mountainous Peloponnese. It is considered one of the oldest Greek tribes which settled in Greece and it was probably a relative tribe of the proto-Greeks who are mentioned by the ancient authors as Pelasgians.^[1] Whilst Herodotus seems to have found the idea that the Arcadians were not Greek far-fetched, it is clear that the Arcadians were considered as the original inhabitants of the region.^[2] This is testified by ancient myths, like the myth of Arcas, the myth of Lycaon etc.

Arcadia is also one of the regions described in the "catalogue of ships" in the Iliad.^[3] Agamemnon himself gave Arcadia the ships for the Trojan war because Arcadia did not have a navy.

Due to its remote, mountainous character, Arcadia seems to have been a cultural refuge. When, during the Greek Dark Age (c. 1200 BC – 800 BC), Doric Greek dialects were introduced to the Peloponnese, the older language apparently survived in Arcadia, and formed part of the Arcado-Cypriot group of Greek dialects. Arcadocypriot never became a literary dialect, but it is known from inscriptions. Tsan is a letter of the Greek alphabet occurring only in Arcadia, shaped like Cyrillic И; it represents an affricate that developed from labiovelars in context where they became t in other dialects.

The Arcadians founded numerous towns. Of these the strongest were the cities which controlled the few fertile valleys; Mantinea, Tegea and Orchomenos. The remaining towns were more mountainous or had smaller plains. Some of these were Asea, Ypsounta, Teuthis, Heraea, Thyraion, Nestani, Alea, Lykosoura, Trikolonon, Tropea, Caphyae, Pallantion, Feneos, Phoezon, etc. From 370 BC the capital of Arcadia became Megalopolis.