Greek refugees is a collective term used to refer to the more than one million Greek Orthodox natives of Asia Minor, Thrace and the Black Sea areas who fled during the Greek genocide (1914-1923) and Greece's later defeat in the Greco-Turkish War (1919–1922), as well as remaining Greek Orthodox inhabitants of Turkey who were required to leave their homes for Greece shortly thereafter as part of the population exchange between Greece and Turkey, which formalized the population transfer and barred the return of the refugees. This Convention Concerning the Exchange of Greek and Turkish Populations was signed in Lausanne, on January 30, 1923 as part of the peace treaty between Greece and Turkey and required all remaining Orthodox Christians in Turkey, regardless of what language they spoke, be relocated to Greece with the exception of those in Istanbul and two nearby islands. Although the term has been used in various times to refer to fleeing populations of Greek descent (primarily after the Ionian Revolt, the Fall of Constantinople or the Greek Civil War), the population strength and the influence of the Asia Minor Greeks in Greece itself, has attached the term to the Anatolian Greek population of the early 20th century. At least 300,000 Greek refugees were from Eastern Thrace, whereas at least 900,000 were from Asia Minor. At least 150,000 were from Istanbul, who left the city in three years before 1928.

The Orthodox Christian refugees from Asia Minor are usually called in Greek simply Οι Πρόσφυγες (Oi Prosfyges, The Refugees). Alternative terms used are Οι Μικρασιάτες πρόσφυγες (Oi Mikrasiates prosfyges, The Asia Minor refugees) or Οι πρόσφυγες του '22 (Oi prosfyges tou '22, The refugees of 1922). Further distinctions are made to denote the refugees from various historic regions of Anatolia: Πόντιοι πρόσφυγες (Pontioi prosfyges, Pontic refugees) from the Black Sea coast, Καππαδόκες πρόσφυγες (Kappadokes prosfyges, Cappadocian refugees) from central Turkey, Μικρασιάτες πρόσφυγες (Mikrasiates prosfyges, The refugees from Asia Minor), to refer to the Greeks from the geographic area of the peninsula; special reference is made for the Refugees from Smyrna (Oi prosfyges tis Smyrnis, Πρόσφυγες της Σμύρνης), since Smyrna was then the second largest Turkish city, and many of the affected Greeks lived there. The refugees from Eastern Thrace are also included.

The eastern coast of the Aegean was inhabited by Greeks as early as the 9th century BC. Aeolian, Ionian and Dorian colonies were established from the Dardanelles to Caria, with the most important being Miletus, Phocaea, Ephesus and Smyrna. The prominence of the Ionians gave to the region the name Ionia. The Greeks of Asia Minor contributed significantly in the ancient Greek history, from the Ionian Revolt, the Ionian League and the conquests of Alexander the Great, to the Hellenistic kingdoms of Pergamos and Pontus. The Ionians were the first Greek-speaking people that the Persians encountered, and the Persian name for Greece became Younan or Yunan (یونان), derived from the word "Ionia." The name spread throughout the Near East and Central Asia.

Following the spread of the Hellenistic civilization in the 3rd century BC, Greek became the lingua franca of Asia Minor, and by the fifth century AD, when the last of the Indo-European native languages of Anatolia ceased to be spoken, Greek became the sole spoken language of the natives of Asia Minor.

After the founding of Constantinople by the first Christian Roman Emperor Constantine the Great in 330, Asia Minor, the major part of the Greek East, became the most important region of the Eastern Roman (Byzantine) Empire. For the centuries to follow, the area was the main manpower and wheat source of the state. Numerous invasions and epidemics (especially the Plague of Justinian) devastated the area in various times. However, Asia Minor remained densely populated, compared to the rest of the Medieval world and held the bulk of the empire's Greek speaking orthodox Christian population. Thus, many renowned Greek-speaking figures who lived during this time were Asia Minor Greeks, including Saint Nicholas (270-343), John Chrysostomos (349-407), Isidore of Miletus (6th century), and Basilios Bessarion (1403-1472). The Greek speaking Christian population began to decline with the invasions of the Muslim Seljuq Turks in the 11th century. The establishment of the Seljuk Empire deprived the Byzantines of a large part of Asia Minor. The Fall of Constantinople on May 29, 1453, and the subsequent fall in 1461 of the Greek Empire of Trebizond, located along the eastern Black Sea coast, marked the end of Greek sovereignty in Asia Minor.

The first centuries of the Ottoman rule were named The Dark centuries by the Greeks. The custom of the Janissaries and the various restrictions on the religious, economic and social lives of the non-Muslim inhabitants of the Empire constituted an imminent danger for the continuation of the Greek inhabitation of Asia Minor. Conditions were improved over the following centuries, but the Greeks remained in the lower caste status of Dhimmi. Islamization and gradual Turkification continued. The ideas of The Enlightenment and the subsequent Greek War of Independence, raised the hopes of the Asia Minor Greeks for sovereignty. Many Greeks from Anatolia fought as revolutionaries and faced the retaliations of the Sultan.

The persecutions, massacres, expulsions, and death marches of the Asia Minor Greeks were renewed during the early 20th century by the Young Turk administration of the Ottoman Empire and during the subsequent revolution of Mustafa Kemal Atatürk. The Ottoman Greek population was severely affected; its misfortunes became known as the Greek Genocide. After the defeat of the Ottoman Empire during World War I, the Allies granted Greece, with the Treaty of Sèvres, the administration of Eastern Thrace (apart from Constantinople) and the city of Smyrna and its environs. The Pontic Greeks attempted to establish their own republic, the Republic of Pontus. The defeat of the Greek army during the Greco-Turkish War led to what became known in Greece as the Asia Minor Catastrophe. A series of events, with the Great Fire of Smyrna been their peak, ended the 3,000-year-old Greek presence in Asia Minor. The Treaty of Lausanne, which was signed in 1923, anticipated the compulsory exchange of populations. The remaining Greek Orthodox population of Asia Minor and Eastern Thrace, as well as the Muslim population of Greece (the Greeks of Constantinople, Imbros and Tenedos and the Muslims of Western Thrace were excluded) were denaturalized from homelands of centuries or millennia.

1914 Ottoman census, which followed the 1909 census, showed a steep decrease of the Greek population by almost 1 million between these years due to loss of lands (with their population) to Greece after the Balkan Wars. The argument that Greeks constituted the majority of the population of Anatolia claimed by Greece during Greco-Turkish War (1919–1922) has been contested by a number of historians. In their book about the British foreign policy of World War I and post war years, Cedric James Lowe and Michael L. Dockrill argued that: Greek claims were at best debatable, [they were] perhaps a bare majority, more likely a large minority in the Smyrna Vilayet, which lay in an overwhelmingly Turkish Anatolia. The estimations of the Ecumenical Patriarchate, the Greek state and various Western sources, place their number much higher. The number of Greeks excluded from the population exchange was about 300,000 (270,000 living in Istanbul). There are not exact figures of the refugee population in Greece.