Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to the east. The Aegean Sea lies to the east of the mainland, the Ionian Sea to the west, and the Sea of Crete and the Mediterranean Sea to the south. Greece has the longest coastline on the Mediterranean basin, spanning thousands of islands and nine traditional geographic regions. It has a population of over 10 million. Athens is the nation's capital and largest city, followed by Thessaloniki and Patras.

Greece is considered the cradle of Western civilisation and the birthplace of democracy, Western philosophy, Western literature, historiography, political science, major scientific and mathematical principles, theatre, and the Olympic Games. The Ancient Greeks were organised into independent city-states, or poleis (singular polis), that spanned the Mediterranean and Black seas. Philip II of Macedon united most of present-day Greece in the fourth century BC, with his son Alexander the Great conquering much of the known ancient world from the Near East to northwestern India. The subsequent Hellenistic period saw the height of Greek culture and influence in antiquity. Greece was annexed by Rome in the second century BC and became an integral part of the Roman Empire and its continuation, the Byzantine Empire, where Greek culture and language were dominant. The Greek Orthodox Church, which emerged in the first century AD, helped shape modern Greek identity and transmitted Greek traditions to the wider Orthodox world.

After the Fourth Crusade in 1204, Greece was fragmented into several polities, with most Greek lands coming under Ottoman control by the mid-15th century. Following a protracted war of independence in 1821, Greece emerged as a modern nation state in 1830. The Kingdom of Greece pursued territorial expansion during the Balkan Wars (1912–1913) and World War I (1914–1918), until its defeat in the Greco-Turkish War in 1922. A short-lived republic was established in 1924 but faced civil strife and the challenge of resettling refugees from Turkey, culminating in a royalist dictatorship in 1936. Greece endured military occupation during World War II, a subsequent civil war, and prolonged political instability, leading to a military dictatorship in 1967. The country began transitioning to democracy in 1974, leading to the current parliamentary republic.

Owing to record economic growth from 1950 to 1973, Greece is a developed country with an advanced high-income economy; its high standard of living has been damaged by a decade-long debt crisis that formed following the 2008 financial crisis. Shipping and tourism are major economic sectors, with Greece being the ninth most-visited country in the world in 2024. Greece is part of multiple international organisations and forums, being the tenth member to join what is today the European Union in 1981. The country's rich historical legacy is reflected partly by its 20 UNESCO World Heritage Sites.

The native name of the country in Modern Greek is Ελλάδα (Elláda^ⓘ, pronounced [eˈlaða] ^ⓘ). The corresponding form in Ancient Greek and conservative formal Modern Greek (Katharevousa) is Ἑλλάς (Hellas, classical: [hel.lás], modern: [eˈlas]). This is the source of the English alternative name Hellas, which is mostly found in archaic or poetic contexts today. The Greek adjectival form ελληνικός (ellinikos, [eliniˈkos]) is sometimes also translated as Hellenic and is often rendered in this way in the formal names of Greek institutions, as in the official name of the Greek state, the Hellenic Republic (Ελληνική Δημοκρατία, [eliniˈci ðimokraˈti.a]).

The English names Greece and Greek are derived, via the Latin Graecia and Graecus, from the name of the Graeci (Γραικοί, Graikoí), one of the first ancient Greek tribes to settle Magna Graecia in southern Italy.

The Apidima Cave in Mani, in southern Greece, has been suggested to contain the oldest remains of early modern humans outside of Africa, dated to 200,000 years ago. However others suggest the remains represent archaic humans. All three stages of the Stone Age are represented in Greece, for example in the Franchthi Cave. Neolithic settlements in Greece, dating from the 7th millennium BC, are the oldest in Europe, as Greece lies on the route by which farming spread from the Near East to Europe.

Greece is home to the first advanced civilisations in Europe and is often considered the birthplace of Western civilisation. The earliest of them was the Cycladic culture which flourished on the islands of the Aegean Sea, starting around 3200 BC, and produced an abundance of folded-arm and other marble figurines. From c. 3100 BC to 1100 BC, Crete, a major cultural and economic centre, was home to the Minoan civilisation known for its colourful art, religious figurines, and monumental palaces. The Minoans wrote their undeciphered language using scripts known as Linear A and Cretan hieroglyphs. On the mainland, the Mycenaean civilisation developed around 1750 BC and lasted until c. 1100 BC. The Mycenaeans possessed an advanced military and built large fortifications. They worshiped many gods and used Linear B to write the earliest attested form of Greek known as Mycenaean Greek.