Civil society is one of the most widely used—and widely maligned—concepts in development studies. In this paper, we argue that much confusion regarding civil society stems from the omnibus nature of its conceptualization. We consider civil society to be an omnibus concept because it has been imbued with several distinct meanings—a normative meaning (civil society as civilized), a functional meaning (civil society as democratizing), and a structural meaning (civil society as a third sector). Using the example of humanitarian NGOs, we demonstrate how the omnibus nature of civil society resists systematization and requires scholars to make problematic assumptions when designing empirical research. As a solution, we propose replacing “civil society” in empirical research with the structural “third-sector” concept. This move narrows the gap between the actors that scholars study and the theoretical construct that they are supposed to represent; it brings the third sector into conceptual alignment with our understanding of the first and second sectors (the market and the state); and it improves our efforts to compare findings across cases and build generalized theories. It also enables scholars to consider questions of power, resources, and influence when studying development NGOs—questions that are difficult to ask when notions of “civil society” are defined as actors that understand, represent, and advocate on behalf of their “constituents.” We conclude that “civil society” as a concept should be maintained for theoretical analyses of what makes society civil but that empirical studies of development are best served by a third-sector approach.