The article focuses on the phenomenon of religious extremism and its dangerous implications on Islam in general, and the Shia system in particular. It highlights the devastating effects it has on religion and Sharia, such as polytheism, Tafwid (man's absolute freedom in actions), extremism, excommunication (takfir), and more. Not only that, but there are also those who seek to sow division and discord among Muslims and confuse true beliefs, tearing apart their unity. This article aims to remove some of this intentional confusion and draw attention to the fact that the Shiite thought or the Twelver Shia system has taken the lead in treating this phenomenon, especially in what Imam al-Ridha (peace be on him) has contributed in this field.The article also offers approaches and treatments. By approaches, we mean the mentioning of some guidelines and criteria that Imam al-Ridha (peace be on him) has established as a theoretical foundation and a key to understanding and analyzing the reality of religious extremism. We analyze and approach to this kind of extremism so that it may be well understood, supporting it with practical applications and treatments. The method followed in this study is an inductive, analytical, applicable method.