Mental ill health is now the most important health issue facing young people worldwide. It is the leading cause of disability in people aged 10–24 years, contributing 45% of the overall burden of disease in this age group. Despite their manifest need, young people have the lowest rates of access to mental health care, largely as a result of poor awareness and help-seeking, structural and cultural flaws within the existing care systems, and the failure of society to recognise the importance of this issue and invest in youth mental health. We outline the case for a specific youth mental health stream and describe the innovative service reforms in youth mental health in Australia, using them as an example of the processes that can guide the development and implementation of such a service stream. Early intervention with focus on the developmental period of greatest need and capacity to benefit, emerging adulthood, has the potential to greatly improve the mental health, wellbeing, productivity, and fulfillment of young people, and our wider society.