The present research work studies the ‘fitnah of takfir’ as one of the most important problems in the Islamic world today. Unfortunately, to achieve their filthy aims, the enemies of Islam, taking the advantages of the ignorance of certain Muslim groups, is trying to skillfully manage and control their jihÁdi movements, which have been actually intended to be against unbelief and Zionists’ acts of aggressions, and motivate the Muslim sects to wage wars against each other. In addition, they set the stage for takfir, which does not have any footing in the orthodox faith of Islam, to find its way into religion and religious sects, taking on the appearance of a great fitnah (sedition) in the Muslim world today. Drawing upon religious and fiqhi texts of religious sects of Islam (whether ShiÝi or Sunni texts), this research work tries to cast light on the nature of the fitnah of takfir on the one hand, and to put forward the fiqhi truthful opinion about those who are involved in leading the fitnah or who play a role in it on the other. It also makes clear the responsibilities of the other Muslim majorities around the world towards this takfiri group. The problem can be put this way: If Muslims are faced with the fitnah of takfir, what strategies can Islamic fiqh formulate to prevent it or lead it to the right direction in order to keep the Muslim community away from the enormous threatening dangers of these extremist takfiri groups?