Erzurum vilayet in the context of Sivas Vilayet

Ottoman Greeks (Greek: Ρωμιοί, romanized: Romioi; Turkish: Osmanlı Rumları) were ethnic Greeks who lived in the Ottoman Empire (1299–1922), a large part of which is in modern Turkey, Greece and the rest of the Balkans. Ottoman Greeks were Greek Orthodox Christians who belonged to the Rum Millet (Millet-i Rum). They were concentrated in eastern Thrace (especially in and around Constantinople), and western, central, and northeastern Anatolia (especially in Smyrna, Cappadocia, and Erzurum vilayet, respectively), in Ottoman Greece and other parts of the Ottoman Balkans, and in Ottoman Cyprus. There were also sizeable Greek communities elsewhere in the Ottoman Armenia, Ottoman Syria and the Ottoman Caucasus, including in what, between 1878 and 1917, made up the Russian Caucasus province of Kars Oblast, in which Pontic Greeks, northeastern Anatolian Greeks, and Caucasus Greeks who had collaborated with the Russian Imperial Army in the Russo-Turkish War of 1828–1829 were settled in over 70 villages, as part of official Russian policy to re-populate with Orthodox Christians an area that was traditionally made up of Ottoman Muslims and Armenians.

The Six Vilayets (Ottoman Turkish: ولايت سته, Vilâyat-ı Sitte), the Six Provinces, or the Six Armenian Vilayets (Armenian: Վեց Հայկական Վիլայեթները Vets' haykakan vilayet'nery; Turkish: Altı vilayet, Altı il) were the main Armenian-populated vilayets ("provinces") of the Ottoman Empire and, together, comprise most of Western Armenia. These were Van, Erzurum, Mamuret-ul-Aziz, Bitlis, Diyarbekir and Sivas.