This chapter provides a summary and review of research concerning the ways in which religion and spirituality (R/S) relate to well-being. A large body of work indicates that R/S provide valued resources (e.g., meaningful orienting systems, social support networks, behavioral regulation skills) and associate with a variety of positive physical and mental health characteristics. Although experimental research is sparse, emerging theoretical models, along with longitudinal studies and mediational studies, have attempted to explain the links between R/S and physical and mental well-being. Additionally, positive R/S coping strategies associate with recovery and healthy adaptation in response to stress and trauma. However, challenges also accompany R/S life naturally. Negative R/S coping strategies associate with poorer adjustment to negative circumstances. Furthermore, R/S struggles, which refer to tensions, conflicts, or negative emotions around R/S matters, occur in several areas: (1) perceived conflict with deities or supernatural evil; (2) interpersonal R/S conflicts with individuals or institutions; and (3) intrapsychic turmoil around morality, doubts about R/S beliefs, or concerns with life meaning. Many R/S struggles are associated with lower levels of health and well-being in both cross-sectional and longitudinal studies. Although R/S struggles involve emotional hardship, preliminary evidence suggests their potential to engender growth and maturity.