In an increasingly complex world, how can public services and social interventions sustain positive outcomes for the people they serve? The sustainability of public services is threatened by the failure of a generation of new public management reforms, from targets and terror to marketisation and competition, to improve outcomes on anything approaching a consistent basis, while often achieving something resembling the very opposite. This book argues for a radical change of course in public service reform. Building on foundational research in public health and social epidemiology, we develop a new theoretical perspective of how social outcomes – those key indicators of societal wellbeing like health, criminal behaviour, or educational attainment – emerge in the human and relational services. We set out a new research and practice agenda: building public service systems capable of engaging meaningfully with the innate complexity of people’s lives. We advance and critically discuss two pragmatic responses to this agenda: Human Learning Systems (HLS) (a complexity-informed approach to public service reform) and Learning Partnerships (a model for research and academic engagement in complex settings). With up-to-date and extensive discussion on public service reform, outcome-based governance and complexity in policy and public administration, this book provides focussed and accessible guidance for both academics and service professionals. We detail a broad and inclusive research agenda which we hope connects those working in research and practice in a shared learning endeavour in years to come.