Rūm millet (millet-i Rûm), or "Roman nation", was the name of the Eastern Orthodox Christian community in the Ottoman Empire. Despite being subordinated within the Ottoman political system, the community maintained a certain internal autonomy.
After the fall of Constantinople to the Ottoman Empire in 1453, all Orthodox Christians were treated as a lower class of people. The Rum millet was instituted by Sultan Mehmet II who set himself to reorganise the state as the conscious heir of the East Roman Empire. The Orthodox congregation was included in a specific ethno-religious community under Graeco-Byzantine domination. Its name was derived from the former Eastern Roman (a.k.a. Byzantine) subjects of the Ottoman Empire, but all Orthodox Greeks, Bulgarians, Albanians, Aromanians, Megleno-Romanians, Romanians and Serbs, as well as Georgians and Arab Melkites, were all considered part of the same millet in spite of their differences in ethnicity and language. Belonging to this Orthodox commonwealth became more important to the common people than their ethnic origins. This community became a basic form of social organization and source of identity for all the ethnic groups inside it and most people began to identify themselves simply as "Christians". However, under Ottoman rule ethnonyms never disappeared, which indicates that some form of ethnic identification was preserved. This is evident from a Sultan's Firman from 1680 which lists the ethnic groups in the Balkan lands of the Empire as follows: Greeks (Rum), Albanians (Arnaut), Serbs (Sirf), "Vlachs" (Eflak, referring to Aromanians, Megleno-Romanians, and Romanians) and the Bulgarians (Bulgar). Christian Armenians who belonged to the Armenian Apostolic Church were not included as they were given a separate millet.
Christians were guaranteed some limited freedoms, but they were not considered equal to Muslims, and their religious practices would have to defer to those of Muslims, in addition to various other legal limitations.