: The Use of al-Maṣlaḥaḥ al-Mursalah Theory in the Fatwā of MUI on the Interfaith Marriage. This article investagates about the concept of al-maṣlaḥaḥ al-mursalah and its relation to the Fatwa of The Council of Indonesian Ulama (MUI). MUI's fatwa states preventing muslim both women and men to marry non-muslims. Whereas no Quranic verses explisitly forbid a marriage between Muslim and Ahl al-Kitāb, even permit it. Thus, the fatwa of MUI can be regarded as driven by socio-political consideration.