Radicalisation is a social and psychological process of incrementally experienced commitment to extremist political or religious ideology. Psychosocial research reveals three frameworks explaining radicalisation: rational choice, social identity, and ideological pathways. Rational choice sees it as fulfilling personal needs and obtaining rewards through the adoption of violent means to achieve one’s goals. Social identity involves becoming aware of the bonds with the group and the development of a strong willingness to sacrifice for the group. Ideology involves the sacralisation of an ideology and the values for which a strong obsession develops, giving rise to a willingness to sacrifice from one’s worldview. This chapter explores these frameworks by assessing their assumptions, key mechanisms, and limitations. The results suggest different proposals for integrating mechanisms from different frameworks.