"Takfiri" is the title used to refer to Islamic groups that use the Takfir movement against their opponents and enemies. These groups, emerging from Salafi movement, today have become the greatest problem in the Muslim world and have caused irreparable damage to the Islamic world. The study intends to study the basis of Takfiri thought in the views of Takfiri groups. This thought is one of the most important basic concepts of Takfiri groups that originated in the early days of Islam. Khawarij was a prominent example. Takfiri groups use this intellectual basis to excommunicate their opponents, including Muslims (Shiites and Sunnis who do not believe in them) and non-Muslims; and besides, they use this thought as a pretext for achieving their political goals and intentions. Although the Wahhabis are actually practicing and propagating this thought, the basis of this view was the appearance of the scholars of the Hadith, including Ahmed Bin Hanbal and his disciple Ibn Taymiyyah, whose followers propagated this thought and was eventually implemented by the Wahhabi sects. Therefore, the Takfiri thoughts that are now in the Islamic world originated from ibn Taymiyya's thoughts and ideas.