Peloponnesus (pĕl´əpənē´səs) or Pelopónnisos (pâ´lôpô´nyēsôs), formerly Morea (mōrē´ə), peninsula (1991 pop. 1,086,935), c.8,300 sq mi (21,500 sq km), S Greece. It is linked with central Greece by the Isthmus of Corinth, and it is washed by the Aegean Sea on the east and southeast, by the Ionian Sea on the southwest and west, and by the gulfs of Pátrai and Corinth on the north. Its deeply indented south coast terminates in Cape Matapan. Mainly mountainous, the region includes the Taygetus, Kyllene, and Erímanthos mts. The Evrótas and Alfiós are the chief rivers.
Predominately agricultural and pastoral, the Peloponnesus produces currants, grapes, figs, citrus fruit, olives, tobacco, and wheat. The most fertile parts of the peninsula are the coastal strips in the north and west. Sheep and goat raising, textile manufacturing, fishing, and sericulture are major sources of income. There are deposits of pyrite, manganese, lignite, and chromium. The peninsula attracts many tourists; the port cities of Pátrai, Corinth, Kalamata, and Návplion are the main modern centers of the Peloponnesus.
Originally populated by Leleges and Pelasgians (said to have been the builders of Mycenae and Tiryns), the peninsula was later occupied by the Achaeans and then by the Dorians, who dominated the Peloponnesus in historic times. The chief ancient divisions of the Peloponnesus were Elis, Achaea, Argolis, and the city-state of Corinth in the north; Arcadia in the center; and Lacedaemonia (comprising Messenia and Laconia) in the south. Sparta, Corinth, Argos, and megalopolis were among its chief cities in ancient times.
With the exception of Achaea and Argos, the whole peninsula participated in the Persian Wars (500–449 BC). At the time of the Peloponnesian War (5th cent. BC) almost the entire peninsula was dominated by Sparta. Spartan hegemony, which after the defeat of Athens extended over all Greece, was broken in the 4th cent. BC by Epaminondas of Thebes, who thus prepared the way for the establishment of Macedonian supremacy over the Peloponnesus by Philip II of Macedon. The Second Achaean League, unable to shake off the Macedonian yoke, was ended in 146 BC by the Roman conquest of the Peloponnesus. Under Roman and Byzantine rule the Peloponnesus was reduced to provincial status and in the centuries that followed was repeatedly raided and invaded by Slavs, Bulgars, and Pechenegs.
When, in 1204, the leaders of the Fourth Crusade established the Latin Empire of Constantinople (see Constantinople, Latin Empire of), the French Villehardouin family received the principality of Achaia or Achaea (i.e., the Peloponnesus) as fief, except for several ports, which passed to Venice. A French feudal state was created and enjoyed a period of great prosperity and chivalrous culture under the Villehardouin princes. Many castles remain to show the unique mixture of French feudal culture and Hellenistic civilization that flourished in the Peloponnesus in the 13th cent. After the death (1278) of William of Villehardouin, the last prince, the principality passed first to the Angevin dynasty of Naples (by marriage), later to various nobles, and in 1383 to a body of Navarrese soldier-adventurers.
The Byzantine Greeks meanwhile had gradually recovered a good part of the peninsula, and in 1432 they achieved complete control. Their triumph, however, was short-lived, for by 1460 Sultan Muhammad II had conquered the peninsula and annexed it to the Ottoman Empire. In the Turko-Venetian Wars from the 15th cent. until the Treaty of Passarowitz (1718), Venice held parts of the Peloponnesus at various times and the entire peninsula from 1687 to 1715. As a result of the Greek War of Independence (1821–29) the peninsula passed to independent Greece.