People with severe mental illness (SMI) face issues of social integration such as finding a job and maintaining social or intimate relationships. The social integration of people with SMI remains high on the political agenda and, since the early 2000s, many countries have developed interventions that specifically targeted it. Despite major reforms in mental health care and the implementation of such interventions, their social integration has, however, remained relatively low and has not much improved over the past decades. Much research has focused on socially inclusive evidence-based practices and interventions, but this thesis shows that factors related to the organisation of services, systems and policies strongly influence the social integration of people with SMI. For better or for worse, social integration is not a clinical outcome, it is a system outcome.