This chapter reviews the philosophical and conceptual foundations of two types of happiness: hedonic well-being and eudaimonic well-being. Both are increasingly the focus of scientific research, including studies of health. We summarize extant evidence linking both types of well-being to health, broadly defined to include self-reported health, disease states and severity, functional capacities and biological risk factors. For eudaimonic well-being, links to brain-based assessments have also been conducted. The overarching message from this literature is that well-being, whether framed as life contentment or life engagement, appears to be protective of good health, and further that health problems appear to compromise well-being. More research is needed, particularly longitudinal studies that can more clearly delineate the direction of causal influences as well as the biological and brain-based mechanisms that account for connections between well-being and health. We conclude with consideration of how studies of well-being might fruitfully intersect with studies of quality of life. A further priority for future work pertains to interventions designed to promote greater experiences of life contentment and life engagement for greater segments of society, which may also be beneficial for health.