Groups experience collective autonomy restriction whenever they perceive that other groups attempt to limit the freedom of their group to determine and express its own identity. We argue that collective autonomy restriction motivates groups (both structurally advantaged and disadvantaged) to improve their power position within the social hierarchy. Four studies spanning real-world (Studies 1 and 2) and lab-based (Studies 3 and 4) intergroup contexts supported these ideas. In Study 1 (N = 311), Black Americans' (a relatively disadvantaged group) experience of collective autonomy restriction was associated with greater support for collective action, and less system justification. In Study 2, we replicated these findings with another sample of Black Americans (N = 292). We also found that collective autonomy restriction was positively associated with White Americans' (a relatively advantaged group, N = 294) support for collective action and ideologies that bolster White's dominant position. In Study 3 (N = 387, 97 groups), groups that were susceptible to being controlled by a high-power group (i.e., were of low structural power) desired group power more when their collective autonomy was restricted (vs. supported). In Study 4 (N = 803, 257 groups) experiencing collective autonomy restriction (vs. support) increased low-power group members' support of collective action, decreased system justification, and evoked hostile emotions, both when groups were and were not materially exploited (by being tasked with more than their fair share of work). Across studies, we differentiate collective autonomy restriction from structural group power, other forms of injustice, group agency, and group identification. These findings indicate that collective autonomy restriction uniquely motivates collective behavior. (PsycINFO Database Record (c) 2019 APA, all rights reserved).