Abū Isḥāq Muḥammad ibn al-Wāthiq (Arabic: أبو إسحاق محمد بن هارون الواثق‎; c. 833 – 21 June 870), better known by his regnal name al-Muhtadī bi-'llāh (Arabic: المهتدي بالله, "Guided by God"), was the Caliph of the Abbasid Caliphate from July 869 to June 870, during the "Anarchy at Samarra".