: Religious Radicalism in the Perspective of Islamic Law. The emergence of ISIS (Islamic State of Iraq and Suriah) movement in some countries, including Indonesia, bring back discussions in the study of religious radicalism. This paper examines the religious radicalism of Islam which is often viewed as religious ideas that could potentially give birth to terrorism. The aspects that were examined here includes religious texts- which are often used as a basis of justification to undertake radical movement-methods in understanding the texts, as well as, the implications for perpetrators of radical movements. This study finds out that the birth of a radical ideology is due to a narrow and incomplete interpretation to the religious texts which l...