The humanitarianism of Sean Penn rests on a wish to promote the well-being of humanity at large rather than American society alone. His humanitarianism is couched within radical politics and cosmopolitanism. Penn’s activism challenges structural readings of celebrity humanitarianism, which broadly situate it within exploitative capitalist relations rather than progressive politics. An assessment of Penn’s humanitarianism can shed light on celebrities’ involvement in the actual conduct of politics, which remains an under-researched area of celebrity studies (Street 2012, pp. 3–4). Contextually, the analysis focuses on Penn’s efforts to assist the victims of Hurricane Katrina in New Orleans in 2005 and the Haitian earthquake in 2010. Both provide insight into Penn’s commitments to justice within and beyond US borders. The chapter makes three claims; first, Penn’s activism points to the centrality of assessing celebrity humanitarianism across contexts to gain insight into the ways in which celebrity messages are localized in one context, and are then transported into another one. Second, Penn’s humanitarian disaster work across contexts illustrates the role of human beings seeking to transform global politics in an equitable direction. The Penn story also brings attention to the practices and discourses of radical celebrity politics grounded in both cosmopolitan values and patriotism. Third, Penn’s humanitarianism can tell us something about the gendered power relations that surround celebrity politics and popular culture more broadly.