Social comparison activity is one of the most important spheres of human functioning; it is necessary for appraising where one stands within his or her community and for establishing viable routes for connecting with others. Social comparison is thus a critical psychological phenomenon essential to understanding both social behavior and formation of identity. To this end, individuals look to similar others to evaluate their own abilities and opinions, look to those better than themselves for inspiration and guidance, and evaluate others depending on similarities and distinctions with the self. In addition, they evaluate their own position in life with reference to other’s positions, look to others for information about social norms and for clues about how to behave, and experience feelings toward others based on implications of mutual differences for their relationship. This renders the nature of social comparisons complex; they take horizontal forms that focus on connections or distinction, as well as vertical forms that focus on superiority or inferiority. Moreover, they may be experienced through interaction, subjectively constructed in one’s mind, or deliberately orchestrated in order to impact others. Complexities of social comparison activity are commensurate with multiple functions that they serve. First, people compare with others in order to gain self-knowledge and reduce uncertainty. Comparisons that fulfill this function typically occur with similar others, are biased toward comparing with those slightly better off, and are sensitive to diagnosticity that information about others carries for oneself. Second, people compare with others in order to self-enhance and protect well-being. Comparisons that fulfill this function often involve contrasting oneself from those worse off, although they can also involve perceiving similarities with superior others, especially when these are role models or close others. Third, people compare in order to self-improve, namely, boost their skills and abilities. Such comparisons typically occur with others that are better, yet similar in relevant attributes, and in domains that leave room for personal progress. Fourth and final, people compare in order to connect socially with others. Such comparisons occur through regular social interaction as individuals emphasize mutual similarities, through creation of comparisons to protect or embolden others, and through selection of social identities that maximize a sense of group belonging.