Abu Ja?far Harun ibn Mu?ammad (Arabic: ??? ???? ????? ?? ???? ????????; 18 April 812 – 10 August 847), better known by his regnal name al-Wathiq Bi’llah (?????? ?????, "He who trusts in God"), was an Abbasid caliph who reigned from 842 until 847 AD (227–232 AH in the Islamic calendar).
Al-Wathiq is relatively obscure both as a ruler and as a person, and his reign is largely considered a continuation of his father's.
The chief events of his reign were the suppression of a Bedouin rebellion in the Hejaz in 845 and an abortive uprising in Baghdad in 846.
The conflict with the Byzantine Empire continued, and the Abbasids even scored a significant victory at Mauropotamos, but after a truce in 845, warfare ceased for several years.