Abstract: This article proposes a way of looking at ownership in which the central conceptual feature is the agreement that brings ownership into existence. On this understanding, ownership is a social fact, and as such derives its legitimacy from the extent to which people living under it give it their uncoerced consent. While any particular system’s substantive features can certainly be judged according to independent moral considerations, these considerations would necessarily be secondary to the facts surrounding the agreement. In rooting legitimacy to consent, the argument runs parallel to both contractualist moral philosophy and ‘externalist’ rights claims, but, as is demonstrated in this article, differs from both in its emphasis on the conceptual centrality of agreement. The latter half of the article explores how this understanding of ownership shifts the grounds for what counts as a legitimate right of property, and then offers a few substantive conclusions regarding particular property rights and the nature of the moral obligations that systems of ownership (so conceived) both create and nullify.