Résumé : This dissertation investigates the social psychological roots of conflicts within social movements. Specifically, we propose that such conflicts can stem from a power struggle between subgroups of social movements. We argue that, to gain power in the form of symbolic and material resources, subgroups need to be recognized as the most prototypical (representative) subgroup of the social movement by third parties. Our research focuses on the reactions of members of established subgroups, previously perceived as prototypical within the movement, to the emergence of ideologically distinct subgroups that attract social recognition (i.e., supplanting subgroups). Precisely, we posit that established subgroup members may perceive competition over prototypicality, with negative consequences on intergroup relations. We conducted qualitative and quantitative studies to examine these dynamics. In Chapter 2, we delved into the intergroup relations, within the French-speaking Belgian feminist movement, between universal and intersectional feminists. Results suggested that intergroup conflicts can be triggered by perception of competition over prototypicality and of symbolic and realistic threats. In Chapter 3 and 4, we experimentally tested these hypotheses through a fictional scenario paradigm. In Chapter 3, we found that supplanting subgroups triggered perception of competition over prototypicality, and symbolic and realistic threats, resulting in negative intergroup relations. In Chapter 4, we experimentally tested the impact of both characteristics of a supplanting subgroup -perceived ideological distinctiveness and ability to attract social recognition - on established subgroup members’ reactions. We found that perceived ideological distinctiveness led to perception of competition over prototypicality and symbolic threat, in turn leading to negative intergroup relations. Moreover, while the perceived ability of an emergent subgroup to attract social recognition had positive impacts on intergroup relations, perception of competition over prototypicality partially buffered them. Finally, in Chapter 5, through a correlational study on the Belgian and French feminist field, we found that a dual identity representation (i.e., the representation of members of different subgroups as distinct entities sharing a superordinate identity) led to more perception of competition over prototypicality and negative intergroup relations. Overall, our hypothesis on the negative effects of perception of competition over prototypicality within social movements was corroborated. This research contributes to the broader literature on conflicts within social movement, offering a nuanced understanding of intra-movement power struggles and their implications for feminist solidarity and cooperation.