Evidence-informed strategies and interventions designed to reduce the likelihood of substance use and related harms. Prevention efforts aim to reduce risk factors and strengthen protective factors at the individual, family, community, and societal levels. These approaches may include education, family and school-based programmes, community initiatives, and policies that promote healthy environments. Prevention can be universal (targeting entire populations), selective (targeting groups at higher risk), or indicated (targeting individuals already showing early signs of risk). By addressing the factors that influence substance use before problems develop or escalate, prevention plays a key role in comprehensive responses to substance use disorders and related social and health challenges.