Reward sensitivity encompasses individual differences in the tendency to detect, pursue, learn from, and derive pleasure from positive stimuli. It is a component of temperament and personality, showing large variations between individuals and moderate consistency within individuals over time. Reward sensitivity shows a distinctive developmental course across the life span, peaking in mid-to-late adolescence. It is biologically based and tied to a system of brain structures that support approach-related emotions, behaviors, and cognitions. It is influenced by genetic and environmental factors and, at high and low levels, is associated with increased risk of numerous psychological disorders. This entry summarizes key features of reward sensitivity, its neural basis, development over the life span, origins, and associations with behavioral health outcomes.