The Greeks or Hellenes (; Greek: Έλληνες, Éllines [ˈelines]) are an ethnic group and nation indigenous to Greece, Cyprus, southern Albania, Anatolia, parts of Italy and Egypt, and to a lesser extent, other countries surrounding the Eastern Mediterranean and Black Sea. They also form a significant diaspora (omogenia), with many Greek communities established around the world.

Greek colonies and communities have been historically established on the shores of the Mediterranean Sea and Black Sea, but the Greek people themselves have always been centered on the Aegean and Ionian seas, where the Greek language has been spoken since the Bronze Age. Until the early 20th century, Greeks were distributed between the Greek peninsula, the western coast of Asia Minor, the Black Sea coast, Cappadocia in central Anatolia, Egypt, the Balkans, Cyprus, and Constantinople. Many of these regions coincided to a large extent with the borders of the Byzantine Empire of the late 11th century and the Eastern Mediterranean areas of ancient Greek colonization. The cultural centers of the Greeks have included Athens, Thessalonica, Alexandria, Smyrna, and Constantinople at various periods.

In recent times, most ethnic Greeks live within the borders of the modern Greek state or in Cyprus. The Greek genocide and population exchange between Greece and Turkey nearly ended the three millennia-old Greek presence in Asia Minor. Other longstanding Greek populations can be found from southern Italy to the Caucasus and southern Russia and Ukraine and in the Greek diaspora communities in a number of other countries. Today, most Greeks are officially registered as members of the Greek Orthodox Church.

Greeks have greatly influenced and contributed to culture, visual arts, exploration, theatre, literature, philosophy, ethics, politics, architecture, music, mathematics, medicine, science, technology, commerce, cuisine and sports. The Greek language is the oldest written language still in use and its vocabulary has been the basis of many languages, including English as well as international scientific nomenclature. Greek was by far the most widely spoken lingua franca in the Mediterranean world and the New Testament of the Christian Bible was also originally written in Greek.