Osman Gazi ben Ertuğrul (Ottoman Turkish: عثمان غازى Osman Ghazi; or Osman Bey or Osman Gazi Han), sometimes transliterated in the past as Othman or Ottoman or Ataman and nicknamed "Kara" ("black" in Turkish), was the leader of the Ottoman Turks and the founder and namesake of the dynasty that established and ruled the Ottoman Empire. The state, while only a small principality (beylik) during Osman's lifetime, would prevail as a world empire under Osman's dynasty for the next six centuries after his death. It existed until the abolition of the sultanate in 1922, or alternatively the proclamation of the Republic of Turkey in 1923, or the abolition of the caliphate in 1924.
Osman announced the independence of his own small principality from the Seljuk Sultanate of Rum in July 27, 1299, and was acclaimed the Khan of the Kayihan tribe. The Ottoman principality was just one of many small Turkish principalities in Anatolia at the time that emerged after the dissolution of the Seljuks, all of which the Ottomans would eventually conquer to reunite Anatolia under Turkish rule. The westward drive of the Mongol invasions had pushed scores of Muslims toward Osman's principality, a power base that Osman was quick to consolidate. As the Byzantine Empire declined, the Ottoman Empire rose to take its place.