Individuals with a stronger sense of purpose in life experience better health across the lifespan. This chapter describes one mechanism linking purpose to health, namely stress reactivity. Across survey, experimental, and daily diary studies, research demonstrates that sense of purpose may yield a homeostatic function, insofar that it helps individuals stay the course to progress toward their purpose in life. Future research is needed to examine how self-regulatory capabilities explain why sense of purpose influences reactivity to stressors and daily events.