Amiru’l Mu’minin

AMIRU ‘L-MU’MININأمير المومنين
“The Commander of the Believers.” A title which was first given to Abdu ‘llah ibn Jahsh after his expedition to Nakhlah and which was afterwards assumed by the Khalifahs (first by ‘Umar) and the Sultans of Turkey. [KHALIFAH.]

Based on Hughes, Dictionary of Islam