The mental health and mental illness continuum, including substance use, addiction and related behaviors, across the lifespan to promote mental health and well-being for individuals, families, communities and diverse populations will be explored. Ethical, historical, social, political, cultural, economic, and environmental determinants of mental health and well-being and their influences on understanding mental health, illness and addiction care will be examined. Theory and research are critically appraised to inform mental health nursing’s knowledge and competencies.