Mental health promotion across the lifespan encompasses evidence-based strategies and interventions designed to enhance psychological well-being and prevent mental disorders from infancy through older adulthood. This chapter explores the theoretical foundations of mental health promotion, including Social Cognitive Theory, Empowerment Theory, and the Health Promotion Model. It examines how socio-economic factors impact mental health at different developmental stages and presents tailored interventions for each life phase. The chapter details age-specific strategies ranging from secure attachment development in early childhood to addressing isolation in older adults. Significant barriers to effective mental health promotion are analysed, including stigma, discrimination, access limitations, knowledge gaps, and cultural factors.