Although it is widely appreciated that rights of exit from a legal order can be important and valuable, there currently exists no adequate account of the relationship between exit rights and legitimacy. This Article cures that deficiency by describing the contribution made by exit rights to the legitimacy of a legal order—a contribution that I call the “exit legitimacy” of that legal order—and offers two accounts of its normative significance. On the “thin” account, exit rights operationalize consent by making it more genuine, more ascertainable, and more closely related to relevant acts and relationships of governance; on the “thick” account, exit rights instantiate a value that I call “political autonomy.” The Article offers grounds to think that, while exit legitimacy is salient in legal orders of all kinds, it is particularly significant for international orders and institutions, which often lack the democratic, traditional, and other legitimating resources available to their national equivalents. Finally, to complete the account of exit legitimacy, the Article considers and responds to four of the strongest objections to which it appears vulnerable. It demonstrates that none of these objections convincingly undermines the case for this unique ground of legitimacy, and that each provides useful guidance for promoting exit legitimacy in legal orders of all kinds.