Abu 'Abdallah Ahmad ibn Abi Du'ad al-Iyadi (Arabic: أبو عبد الله أحمد بن أبي دؤاد الإيادي‎, romanized: ʾAbū ʿAbd Allāh ʾAḥmad ibn ʾAbī Duʾād al-ʾIyādī) (776/7–June 854) was an Islamic religious judge (qadi) of the mid-ninth century. A proponent of Mu'tazilism, he was appointed as chief judge of the Abbasid Caliphate in 833, and became highly influential during the caliphates of al-Mu'tasim and al-Wathiq. During his tenure as chief judge he sought to maintain Mu'tazilism as the official ideology of the state, and he played a leading role in prosecuting the Inquisition (mihnah) to ensure compliance with Mu'tazilite doctrines among officials and scholars. In 848 Ibn Abi Du'ad suffered a stroke and transferred his position to his son , but his family's influence declined during the caliphate o