This review aims to systematically evaluate the available evidence on the effectiveness of various interventions aimed at reducing violent radicalisation and terrorism. Quantitative analysis will be employed to assess the overall impact and identify the factors that influence it. The key research questions are: (1) What interventions are successful in preventing or reducing violent radicalisation and terrorism? (A successful intervention will be defined as one that effectively reduces cognitive radicalisation (e.g., extremist beliefs or ideological commitment), reduces behavioural radicalisation (e.g., intentions or actions related to violent extremism), prevents at-risk individuals from becoming radicalised (counter-radicalisation), or facilitates the disengagement and de-radicalisation of individuals already involved in extremist activities or networks) (2) Are certain preventive strategies more effective than others? (3) How do participants’ characteristics influence programme outcomes? (4) How do the features of interventions, their implementation, and methodologies impact the effectiveness of terrorism prevention? The review will conduct analyses considering participant characteristics (e.g., age, gender, risk level), intervention components (e.g., theoretical foundations, theory of change), implementation (e.g., facilitator training, dosage), and methodological aspects (e.g., study design). The goal is to identify the most effective interventions, the target groups they work for, and the conditions under which they are most successful.