People who feel bored experience that their current situation is meaningless and are motivated to reestablish a sense of meaningfulness. Building on the literature that conceptualizes social identification as source of meaningfulness, the authors tested the hypothesis that boredom increases the valuation of ingroups and devaluation of outgroups. Indeed, state boredom increased the liking of an ingroup name (Study 1), it increased hypothetical jail sentences given to an outgroup offender (Study 2 and Study 3), especially in comparison to an ingroup offender (Study 3), it increased positive evaluations of participants' ingroups, especially when ingroups were not the most favored ones to begin with (Study 4), and it increased the appreciation of an ingroup symbol, mediated by people's need to engage in meaningful behavior (Study 5). Several measures ruled out that these results could be explained by other affective states. These novel findings are discussed with respect to boredom, social identity, and existential psychology research.