Although it is a part of the wider Mediterranean region, the Adriatic Sea is for many reasons rightly considered a marine subregion in its own right. This chapter provides a concise overview of key recent developments and challenges of the Adriatic Sea, many of which concern Adriatic subregional features. While some of these features were well-known in the earlier history of the law of the sea, they are now re-emerging in a new and more complex contemporary setting. The coastal states of the Adriatic Sea are now facing major challenges as regards the sustainability of marine resources, where impacts in one Adriatic area may be reflected in any other area of that sea. Simultaneously, complex regional responses to the uses of the seas are being developed within the European Union (EU) in the context of its Integrated Maritime Policy as well as on the basis of the EU Marine Strategy Framework Directive. Regionalization of the "European seas," including a subregional approach where appropriate, is an important element of the EU Marine Strategy. Is there a role for the EU, now also equipped with its Marine Strategy, to play in the current Adriatic Sea situation? How has the EU handled pressing Adriatic Sea issues so far, especially in relations between EU member states and states that are candidates for EU membership? Are there specific Adriatic Sea "subregional" approaches emerging in that context? And if so, how do they relate to the international law framework provided by the United Nations Convention on the Law of the Sea? Some of those questions still remain without definitive answers. This chapter aims to help us understand why such a situation has persisted.