Recent years have seen renewed attention to curiosity and interest―recognizing, seeking out, and preferring things that are outside of one’s normal experience. In this chapter, we explore curiosity, where it fits in the larger scheme of positive emotions, how individual differences are assessed, the advantages of being curious in social relationships, links between curiosity and elements of well-being, and how it has been used in interventions to improve people’s quality of life. Our review emphasizes findings that show how curiosity operates in the laboratory and everyday life, and how, under certain conditions, curiosity can be a profound source of strength, or a liability. People who are regularly curious and willing to embrace the novelty, uncertainty, and challenges that are inevitable in everyday life have an advantage in creating a fulfilling existence compared with their less curious peers. Our review is designed to bring further attention to this underappreciated human universal.