We propose that people treat prejudice as more legitimate when it seems rationalistic-that is, linked to a group's pursuit of collective interests. Groups that appear to be coherent and unified wholes (entitative groups) are most likely to have such interests. We thus predicted that belonging to an entitative group licenses people to express prejudice against outgroups. Support for this idea came from 3 correlational studies and 5 experiments examining racial, national, and religious prejudice. The first 4 studies found that prejudice and discrimination seemed more socially acceptable to third parties when committed by members of highly entitative groups, because people could more easily explain entitative groups' biases as a defense of collective interests. Moreover, ingroup entitativity only lent legitimacy to outgroup prejudice when an interests-based explanation was plausible-namely, when the outgroup could possibly threaten the ingroup's interests. The last 4 studies found that people were more willing to express private prejudices when they perceived themselves as belonging to an entitative group. Participants' perceptions of their own race's entitativity were associated with a greater tendency to give explicit voice to their implicit prejudice against other races. Furthermore, experimentally raising participants' perceptions of ingroup entitativity increased explicit expressions of outgroup prejudice, particularly among people most likely to privately harbor such prejudices (i.e., highly identified group members). Together, these findings demonstrate that entitativity can lend a veneer of legitimacy to prejudice and disinhibit its expression. We discuss implications for intergroup relations and shifting national demographics. (PsycINFO Database Record (c) 2015 APA, all rights reserved).