Social support has always been central to midwifery practice, but there is concern that its role has diminished in the recent past because of the continuing fragmentation and medicalisation of care. The meaning of social support is broad and diffuse, making it difficult to define and study. Nonetheless, there is considerable evidence that levels of social support have a major impact on health and there are a number of theories and mechanisms that have been put forward to explain this. This chapter discusses the meaning of social support and related concepts, and reviews the theoretical underpinnings and research evidence as to its effectiveness and its relevance to the transition and experience of childbirth. It also discusses the balance between professional interventions and ordinary sources of support, noting that the evidence does not always suggest that health professionals are the best providers of social support.