Uthman or Othman, c.574-656, 3d caliph (644-56), also known as Uthman ibn al-Affan; son-in-law of Muhammad. He belonged to the great Umayyad family and was selected as caliph after the murder of Umar. Muslim conquests were continued and extended to Bactria and Cyprus. To strengthen his control over the distant provinces, he replaced the generals and governors appointed by Abu Bakr and Umar with members of his own family. Uthman ordered the compilation of the first official version of the Qur'an. In 656 a mob of malcontents in Medina stormed Uthman's house and murdered him. Ali succeeded to the caliphate. Osman is the Turkish form of Uthman.