The Peloponnese (/ˈpɛləpəˌniːz/) or Peloponnesus (/ˌpɛləpəˈniːsəs/; Greek: Πελοπόννησος, Pelopónnēsos) is a peninsula and geographic region in southern Greece. It is separated from the central part of the country by the Gulf of Corinth. During the late Middle Ages and the Ottoman era, the peninsula was known as the Morea (Greek: Μωρέας), a name still in colloquial use in its demotic form (Μωριάς).
The peninsula is divided among three administrative regions: most belongs to the Peloponnese region, with smaller parts belonging to the West Greece and Attica regions.
It was here that the Greek War of Independence began in 1821. The Peloponnesians have almost totally dominated politics and government in Greece since then.
The Peloponnese is a peninsula that covers an area of some 21,549.6 square kilometres (8,320.3 sq mi) and constitutes the southernmost part of mainland Greece. While technically it may be considered an island since the construction of the Corinth Canal in 1893, like other peninsulas that have been separated from their mainland by man-made bodies of waters, it is rarely, if ever, referred to as an "island". It has two land connections with the rest of Greece, a natural one at the Isthmus of Corinth, and an artificial one by the Rio-Antirio bridge (completed 2004).
The Peloponnese region (Greek: Περιφέρεια Πελοποννήσου), is a region in southern Greece. It borders the West Greece region to the north and Attica to the north-east. The region has an area of about 15,490 km². It covers most of the Peloponnese peninsula, except for the northwestern subregions of Achaea and Elis which belong to West Greece and a small portion of the Argolid peninsula that is part of Attica.
The Peloponnese region was established in the 1987 administrative reform. With the 2010 Kallikratis plan, its powers and authority were redefined and extended. Along with the West Greece and the Ionian Islands regions, it is supervised by the Decentralized Administration of the Peloponnese, Western Greece and the Ionian Islands based at Patras. The region is based at Tripoli and is divided into five regional units (pre-Kallikratis prefectures), Arcadia, Argolis, Corinthia, Laconia and Messenia, which are further subdivided into 26 municipalities. The largest city of the region is Kalamata.
The Theme of the Peloponnese (Greek: θέμα Πελοποννήσου) was a Byzantine military-civilian province (thema, theme) encompassing the Peloponnese peninsula in southern Greece. It was established in c. 800, and its capital was Corinth.
From 27 BC until the end of the 6th century, the Peloponnese formed part of the province of Achaea, which during Late Antiquity comprised also the eastern parts of Central Greece. Its capital was Corinth.