Erzurum Vilayet

The Vilayet of Erzurum () was a first-level administrative division (vilayet) of the Ottoman Empire.
The vilayet of Erzurum shared borders with the Persian and Russian empires in the east and north-east, in the north with the Trebizond Vilayet, in the west with the vilayet of Sivas, and in the south with the vilayets of Bitlis, Mamuret-ül Aziz and Van.
At the beginning of the 20th century, Erzurum Vilayet reportedly had an area of , while the preliminary results of the first Ottoman census of 1885 (published in 1908) gave the population as 645,702. The accuracy of the population figures ranges from "approximate" to "merely conjectural" depending on the region from which they were gathered. It was one of the six Armenian vilayets in the eastern part of Anatolia, and, prior to World War I, many Armenians lived there as did Georgians, Pontic Greeks and Caucasus Greeks, and other ethnic groups, both Muslim and Christian [mainly Greek Orthodox and Armenian Apostolic (Orthodox/Gregorian)].
History.
The Erzurum Eyalet was one of the first Ottoman provinces to become a vilayet after an administrative reform in 1865, and by 1867 it had been reformed into the Erzurum Vilayet.
In 1875 it was divided in six vilayets: Erzurum, Van, Hakkari, Bitlis, Hozat (Dersim) and Kars-Çildir. In 1888 by an imperial order Hakkari was joined to the vilayet of Van, and Hozat to Mamuret ul-Aziz.
The Kars and Çildir regions were lost in the Russo-Turkish War (1877–1878) and ceded to the Russian Empire, which administered it as the Kars Oblast until 1917.
Administrative divisions.
Sanjaks of the vilayet: 
Demographics.
In 1893, there were in total 19 Kaza (districts). In all kaza's Muslims (Sunni and Alevi) were the majority. Lowest percentage of Muslims (64%) was in the kaza of Hınıs. Most of the Protestants and Catholics were Armenian.