The main claim of this Essay, prepared for the Research Handbook on Private Law Theories, is that only grounding property in liberalism’s fundamental commitment to individual self-determination can secure its legitimacy. I do not deny that property systems assign private authority over resources in numerous different ways. But appreciating the heavy legitimacy burden which haunts property implies that for owners’ authority to be justified, property must both rely upon and be guided by its service of people’s right to self-determination, which is - in a liberal polity - our most fundamental right. This means that in a liberal polity the commitment to individual autonomy does not only dominate property’s justification. It also significantly shapes property’s constitution and thus grounds its most fundamental legal features. The essay offers a sketch of this distinctively liberal conception of property, which I develop more fully in my book, A Liberal Theory of Property (forthcoming 2020). I begin by discussing the way in which property both empowers and disables, enhances people’s autonomy and renders them vulnerable. This implies that a background regime that secures for everyone the preconditions of autonomy - health, education, and means of subsistence, as well as property - is necessary for property to be legitimate. But it is not sufficient. In a genuinely liberal polity, law follows the three pillars of the autonomy-enhancing conception of property: (1) it carefully circumscribes owners’ private authority so that it follows its contribution to self-determination; (2) it includes a structurally pluralist inventory of property types so as to offer people real choice; and (3) it follows the prescriptions of relational justice so as to ensure that ownership does not offend the maxim of reciprocal respect for self-determination on which property’s legitimacy is grounded. By founding property on people’s right to self-determination, a genuinely liberal law insists that property must comply with these three pillars: carefully delineated private authority, structural pluralism, and relational justice. There are admittedly (sometimes significant) gaps between the ideal of liberal property and the life of property in liberal societies. These blemishes, however, offer the theory’s most valuable promise, because they must be treated as a source of internal critique. They point out to the most urgent remedial action that is needed for property law in order for it to conform with its autonomy-enhancing premise.