The end of the Cold War and the ‘War on Terror’ has signalled a shift in the security policies of all states. It has also led to the reconsideration of the policy of neutrality, and what being neutral means in the present age. This book examines the conceptualisation of neutrality from the Peloponnesian War to today, uncovering how neutrality has been a neglected and misunderstood subject in International Relations (IR) theory and politics. By rethinking neutrality through constructivism, this book argues that neutrality is intrinsically linked to identity. Using Sweden as a case study, it links identity, sovereignty, internationalism and solidarity to the debates about Swedish neutrality today and how neutrality has been central to Swedish identity and its worldview. It also examines the challenges to Swedish neutrality and neutrality broadly, in terms of European integration, globalisation, the decline of the state and sovereignty, and new threats to security, such as international terrorism, arguing that the norms and values of neutrality can be reworked to contribute to a more cosmopolitan international order.