After outlining the key aspects of the changing social, cultural, and policy context of parenting in Western societies, the introduction clarifies terminology and key concepts used throughout the book, such as the distinction among fatherhood, fathering, and types of fathers. It also presents the theoretical framework used to examine father involvement with young children in six countries. This includes the fatherhood regime, fathers’ agency gap and capability to care for children, and gendered care and workplace cultures. In addition, the structural context of welfare states and policy regimes is reviewed to frame the institutional support for father involvement, such as compensated paternity and parental leave. At the individual level father involvement is conceptualized as encompassing engagement, accessibility and responsibility as expressed in the type and quantity of time of fathers’ activities with their young children. Finally, the chapter briefly outlines the structure of the book.