Radicalization (or radicalisation) is the process by which an individual or a group comes to adopt increasingly radical views in opposition to a political, social, or religious status quo. The ideas of society at large shape the outcomes of radicalization; for example, radical movements can originate from a broad social consensus against progressive changes in society or from a broad desire for change in society. Radicalization can result in both violent and nonviolent action – academic literature focuses on radicalization into violent extremism (RVE) or radicalisation leading to acts of terrorism. Multiple separate pathways can promote the process of radicalization, which can be independent but are usually mutually reinforcing.

Radicalization that occurs across multiple reinforcing pathways greatly increases a group's resilience and lethality. Furthermore, by compromising a group's ability to blend in with non-radical society and to participate in a modern, national or international economy, radicalization serves as a kind of sociological trap that gives individuals no other place to go to satisfy their material and spiritual needs.