This chapter reviews research investigating physiological correlates of mental well-being including both hedonic and eudaimonic orientations of well-being and their common measures. This review makes it clear that there are consistent associations between different physiological systems and hedonic wellbeing in terms of positive affect; findings on the physiology of life satisfaction are unconvincing. Research investigating eudaimonic well-being is inconclusive but suggests that there are physiological correlates of psychological well-being. In particular, meaning, one of the dimensions of psychological well-being turns out to be strongly associated with physiology. This chapter concludes that additional research is needed to further clarify the physiological underpinnings of various aspects of mental well-being including both hedonic and eudaimonic orientations.