The growth of radical armed groups in the West Asia - North Africa (WANA) region has impelled academic and policy interest in radicalisation pathways and their drivers. 1 But while radicalisation models usually incorporate identity-related factors, identity itself is rarely a central focus. To fill this gap, this literature review examines a specific area of social psychology – Social Identity Theory (SIT) – to explain how identity and related nuances of group membership, depersonalisation, and self-esteem, can operate to transform individuals into radicals. SIT research has facilitated the development of a rich literature on intergroup relations in the context of religious2 and ethnic conflicts,3 as well as the linkages between terrorism and group dynamics. 4 Social psychologists, such as Reicher and Haslam, have linked radicalisation, extremism, and group processes: “we are learning that radicalisation does not happen in a vacuum, [and that it is] driven in part by rifts among groups that extremists seek to create, exploit and exacerbate.”5 Reciprocally, terrorism studies have also begun to offer insights into how intergroup relations affect behaviour. One outcome is the proliferation of theories that seek to explain intergroup dynamics in conflict contexts, including Social Exclusion Theory,6 Optimal Differentiation Theory,7 Terror Management Theory8 and Optimal Distinctiveness Theory.9 This review begins by briefly defining three key terms (Identity, Social Identity, and Role Identity), after which it explains the focus on SIT in this review. Because the role of identity in radicalisation is highly contextual, the review starts by discussing how instability and uncertainty influence social identity. It then moves to examine key concepts including belonging, collective identity, resistance identity, alternative identities, and social mobility. Through this, it seeks to elaborate on the important role that social identity can play in radicalisation processes. The review also acknowledges how the modernity crisis in the WANA region has led to the rise of radical groups through their consolidation of a unique and attractive collective identity. Finally, areas of future research are suggested at the end of this review to assist in understanding the phenomenon further and in developing P/CVE efforts. This review offers new insights into the identity dimensions of radicalisation, for the benefit of Preventing and Countering Violence Extremism (P/CVE) efforts, as well as future research. It should be used as a guide for policy makers and P/CVE stakeholders so that they may better understand the radicalisation process, and design appropriate and effective P/CVE initiatives. The same concepts should also guide efforts on returnee rehabilitation and reintegration. This review is written as part of the project “Religion for Peace and Development in the WANA Region,” and should be read in tandem with related WANA Institute research on radicalisation drivers among youth in Jordan,10 and psychological drivers of radicalisation.