Chapter 11 addresses terrorist violence as a special form of intergroup conflict that has plagued the world for many years with little sign of abatement. Terrorism is defined as the commitment of acts of violence by non-state actors, perpetrated against civilian populations, intended to cause fear, in order to achieve a political objective. Psychological research is presented that seeks to explain why people are attracted to terrorism to the point of sacrificing their own life, but also why out of a large number of disenchanted individuals, only few end up committing terrorist acts of violence. The question why and under what conditions terrorists find support for their violent actions in their communities is also discussed. Terrorist attacks elicit changes in attitudes, behaviour, and mental health in the targeted communities and beyond. Research is presented showing how the experience or fear of terrorist violence affects people’s attitudes, behaviours, and psychological well-being. The chapter ends with a discussion of strategies for reducing the likelihood of terrorist violence informed by social psychological theories of intergroup behaviour.