Many scholars worldwide have pondered the intriguing subject of why people resort to terrorism and what drives them to carry on with it despite the dangers to their safety, which has given rise to numerous hypotheses and assumptions. Numerous theories, including organisational, psychological, sociological, environmental, and instrumental theories, have been attempted to explain terrorism while taking into account individual, social, and economic aspects. Though many theories attempted to explain terrorism, major theories were focused on this chapter. Psychodynamic perspectives (identity theory, narcissism theory, paranoia theory, absolutist/apocalyptic theory, and frustration-aggression theory), psychopathological theories, sociological theories, and other relevant theories were explained in this chapter. Terrorism theories are diverse and complex, reflecting the intricate nature of the phenomenon. There is no single, universally accepted explanation, and research usually concentrates on particular aspects like motivations, organisational structures, or socio-political contexts. To be effective, counter-terrorism strategies must recognise different theoretical perspectives and adapt responses to specific situations, since a one-size-fits-all approach is unlikely to succeed.