Market freedom consists in the ability to impose costs on other people without being responsible to them for doing so. A market is a domain of conduct in which people who enjoy this privilege interact with each other. This understanding of market freedom has three notable advantages. First, it clarifies and broadens our conception of what a market is by showing that market freedom is enjoyed in a wide range noncommercial contexts, and that rights of possession and exchange, systems of incentives, and so on are not constitutive features of markets but contingent constraints on them. Second, it clarifies and broadens our understanding of the value of market freedom by showing that it is a necessary condition for the pursuit of traditional liberal ends such as limited government, social progress, and personal development. Third, it clarifies our understanding of the limits of market freedom by showing that in a liberal polity markets have to be authorized by republican means and constrained by various republican (responsibility-promoting) mechanisms.