Objective With increasing life expectancy, there is a focus on "healthy ageing". Most activities in this area focus on the elderly. However, the ageing process starts much earlier. Childhood offers an important window to lay a base for future healthy ageing. Thus, to address the full ageing process, we should include younger populations in ageing research. If we aim for healthy ageing across the life course, we need to clarify the meaning of health at different ages. The aim of this paper was to develop a conceptual framework for child health, which can be used as a starting point for healthy ageing research from a life course perspective. Results We conceptualize child health as: "a dynamic state, not merely the absence of disease or disability, but also adequate resilience that permits optimal physical, mental, and social functioning, and optimal quality of life in order to achieve full potential and to become an independent, functional, and social individual." We propose five core dimensions of child health: Absence of physical disease; absence of psychiatric disorders; optimal physical, mental, and social functioning, including adequate development; good quality of life or well-being; and adequate resilience. Conclusion This conceptualization of child health and its dimensions can be seen as a first step towards building a framework for future studies into healthy ageing across the life course.