Guided by existing brand-activism literature, this study investigates the rising phenomenon of brands taking a public stance on controversial issues to advocate for societal changes. Based on one-on-one, in-depth interviews, this study delineates the conceptual differences between brand activism and corporate social responsibility (CSR), proposes a new conceptualization of brand activism, and explicates consumers’ responses to brand activism acts. We propose a new conceptualization of brand activism, defined as values-based, controversial, focused on external communications, and driven by public interest. We also unpack factors that potentially shape consumers’ perceptions of authenticity in brand activism activities—measurable action, brand-cause fit, and consistency. Furthermore, we explore consumers’ responses to brand-activism acts and show that consumers generally rate these actions favorably. The study offers a comprehensive conceptualization of brand activism that is empirically substantiated and explicates factors shaping its perceived authenticity and consumer reactions. These findings advance current literature on brand activism and CSR.