This article presents a theoretical model of thriving through relationships, emphasizing the role of close relationships in promoting well-being. It highlights two life contexts through which people may thrive: coping successfully with adversity and actively pursuing opportunities for growth and development. The model proposes two relational support functions—Safe Haven and Source of Strength (SOS)—that are fundamental to thriving in each context. It also identifies mediators through which relational support is likely to have long-term effects on thriving. The article argues for a new perspective on social support, conceptualizing it as an interpersonal process focused on thriving rather than just stress-buffering. It emphasizes the importance of support provision in life contexts other than adversity and identifies specific mediators that explain the link between support and long-term thriving outcomes. The article also discusses the components of thriving, including hedonic and eudaimonic well-being, psychological well-being, social well-being, and physical well-being. It highlights the importance of support functions in promoting thriving through adversity and in supporting participation in life opportunities in the absence of adversity. The article concludes by emphasizing the importance of responsive and sensitive support in promoting thriving and the need for future research on the effects of relational support on thriving.This article presents a theoretical model of thriving through relationships, emphasizing the role of close relationships in promoting well-being. It highlights two life contexts through which people may thrive: coping successfully with adversity and actively pursuing opportunities for growth and development. The model proposes two relational support functions—Safe Haven and Source of Strength (SOS)—that are fundamental to thriving in each context. It also identifies mediators through which relational support is likely to have long-term effects on thriving. The article argues for a new perspective on social support, conceptualizing it as an interpersonal process focused on thriving rather than just stress-buffering. It emphasizes the importance of support provision in life contexts other than adversity and identifies specific mediators that explain the link between support and long-term thriving outcomes. The article also discusses the components of thriving, including hedonic and eudaimonic well-being, psychological well-being, social well-being, and physical well-being. It highlights the importance of support functions in promoting thriving through adversity and in supporting participation in life opportunities in the absence of adversity. The article concludes by emphasizing the importance of responsive and sensitive support in promoting thriving and the need for future research on the effects of relational support on thriving.