Examining the nebulous and changing definitions of extremism and religious extremism, this systematic literature analysis highlights enduring definitional issues that impede advancement in both academia and politics. After screening 510 records from Web of Science and Scopus using the PRISMA 2020 framework and SPIDER tool, the current research used theme synthesis to analyze 11 papers published between 2018 and 2023. Four sub-themes and three main themes—belief, behavior, and definitional ambiguity—elucidate the intolerance and ideological rigidity that underlie extremist acts. Doctrinal manipulation used to excuse violence or exclusion is a hallmark of religious extremism. Calls for interdisciplinary cooperation and context-sensitive frameworks are prompted by the complexity of legal and societal reactions caused by the lack of a universal definition. In order to address the underlying roots of extremism, the report recommends long-term approaches centered on social transformation, education, and democratic ideals.
