Abstract: Drawing on social identity theory (SIT), this study explored social class group identity, intergroup attitudes, and views about social mobility and inequality among socioeconomically and racially/ethnically diverse adults in the U.K. (n = 457) and the U.S. (n = 595). U.K. participants evidenced greater consensus about the social class groups present in their society than did U.S. participants, but lower, working, middle, and upper class were commonly perceived in both contexts, and many participants self‐identified as working class (38% U.K., 17% U.S.) or middle class (45% U.K., 47% U.S.) Consistent with SIT, participants in both contexts identified with their social class ingroup (e.g., felt they belonged) and stereotyped it less harshly on dimensions (warmth or competence) on which it was generally negatively stereotyped. Importantly, middle and upper class participants tended to feel more positively (e.g., proud) about their ingroup, and believed society was more fair and equal, and upward mobility more likely, than did lower and working class participants.