Republicans have traditionally viewed the private realm with a degree of suspicion, wary that the right to privacy might be claimed by individuals to evade their civic responsibilities. This thesis explains why republicans ought to value individual privacy. The core value in contemporary republican thinking is a particular conception of freedom - the absence of domination.Privacy serves this conception of freedom in two broad ways. It shields those who have it from domination by others. But it is also essential to what republicans consider the most effective means of securing conditions of freedom - a participatory form of self-government. Republicans take the view that the citizens of a political community can only be assured of conditions of freedom by participating in the political processes that generate the laws that regulate their lives.The thesis explains that privacy is essential to effective political participation. Although participation in political decision-making requires individuals to engage at some point in public dialogue, deliberation among a more restricted group may be an essential preliminary to this, and a right to privacy provides the boundaries that make such deliberation possible. However, a life cannot be led entirely in public, and an agent’s capacity to engage effectively in political life (or, perhaps, to engage in it at all) will depend on her having developed an autonomous way of life generally. But privacy is a pre-requisite for the development of such a life. According to the account developed in this thesis then, privacy is to be understood as a pervasive and collective good, both secured by and essential to political participation.