Page "Caliphate" Paragraph 6

According to Sunni Muslims, the first caliph to be called Amir al-Mu ' minin was Abu Bakr Siddique, followed by Umar ibn al-Khattāb, the second of the Four Rightly Guided Caliphs.

Uthman ibn Affan and Ali ibn Abi Talib also were called by the same title, while the Shi ' a consider Ali to have been the only truly legitimate caliph.