The Peloponnese 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, a name still in colloquial use in its demotic form.
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 peninsula has been inhabited since prehistoric times. Its modern name derives from ancient Greek mythology, specifically the legend of the hero Pelops, who was said to have conquered the entire region.
The name Peloponnesos means "Island of Pelops".
The Mycenaean civilization, mainland Greece's (and Europe's) first major civilization, dominated the Peloponnese in the Bronze Age from its stronghold at Mycenae in the north-east of the peninsula.
The Mycenean civilization collapsed suddenly at the end of the 2nd millennium BC. Archeological research has found that many of its cities and palaces show signs of destruction. The subsequent period, known as the Greek Dark Ages, is marked by an absence of written records.
In 776 BC, the first Olympic Games were held at Olympia, and this date is sometimes used to denote the beginning of the classical period of Greek antiquity. During classical antiquity, the Peloponnese was at the heart of the affairs of ancient Greece, possessed some of its most powerful city-states, and was the location of some of its bloodiest battles.
The major cities of Sparta, Corinth, Argos and Megalopolis were here, and was the homeland of the Peloponnesian League. Soldiers from the peninsula fought in the Persian Wars and was the scene of the Peloponnesian War of 431–404 BC. It fell to the expanding Roman Republic in 146 BC and became the province of Achaea. During the Roman period, the peninsula remained prosperous but became a provincial backwater, relatively cut off from the affairs of the wider Roman world.
After the partition of the Empire in 395, the Peloponnese became a part of the East Roman or Byzantine Empire. The devastation of Alaric's raid in 396–397 led to the construction of the Hexamilion wall across the Isthmus of Corinth.
Through most of Late Antiquity, the peninsula retained its urbanized character: in the 6th century, Hierocles counted 26 cities in his Synecdemus. By the latter part of that century, however, building activity seems to have stopped virtually everywhere except Constantinople, Thessalonica, Corinth and Athens.
This has traditionally been attributed to calamities such as plague, earthquakes and Slavic invasions.
However, more recent analysis suggests that urban decline was closely linked with the collapse of long-distance and regional commercial networks that underpinned and supported late antique urbanism in Greece, as well as with the generalized withdrawal of imperial troops and administration from the Balkans.