Objectification is a notion central to contemporary feminist theory. It has famously been associated with the work of anti-pornography feminists Catharine MacKinnon and Andrea Dworkin, and more recently with the work of Martha Nussbaum. However, objectification is a notion that has not yet been adequately defined. It has been used rather vaguely to refer to a broad range of cases involving, in some way or another, the treatment of a person (usually a woman) as an object. My purpose in this paper is to offer a plausible understanding of objectification. I do that by focusing on the work of four prominent thinkers: Immanuel Kant, and contemporary feminists Catharine MacKinnon, Andrea Dworkin and Martha Nussbaum. Through drawing on these thinkers' conceptions of objectification, I am finally led to a more complete and coherent understanding of this notion.