The present studies examined the hypothesis that loss of personal significance fuels extremism via the need for cognitive closure. Situations of significance loss—those that make one feel ashamed, humiliated, or demeaned—are inconsistent with the desire for a positive self-image, and instill a sense of uncertainty about the self. Consequently, individuals become motivated to seek certainty and closure that affords the restoration of personal significance. Extremist ideologies should thus increase in appeal, because they promise clear-cut strategies for such restoration. These notions were supported in a series of studies ranging from field surveys of political extremists imprisoned in the Philippines (Study 1) and Sri Lanka (Study 2) to experiments conducted with American samples (Studies 3–4). Implications of these findings are considered for the psychology of extremism, and for approaches to counterradicalization, and deradicalization.