The aim of this chapter is to give an overview of the general field of youth mentoring and its application within the context of children in care. The introduction sets down the underpinning assumption of the book that both formal and informal support systems are essential and that many young people benefit from having supportive adult (non-parental) relationships in their lives. We acknowledge that adolescence itself is one of the most busy and complex transition periods in life and recognise that for a young person in care, the challenges are often heightened. We note that formal supports for children in care, such as social work, have become increasingly aware of the importance of relationship-based work with young people but are limited in their capacity to provide an enduring relationship for a child in the same way that informal supporters can. Formal supports like social work can, however, facilitate young people to enhance their informal support networks, and youth mentoring can be a means of doing so. A brief sketch of the theoretical rationale for youth mentoring is provided, incorporating Jean Rhodes’s model of mentoring (2005), social support, coping, resilience, relational cultural theory and social capital. The chapter ends with a synopsis of the book content.