In the last decade, the European Union has been increasingly active in the maritime domain. Based on the achievements that the European Union has accomplished in the international maritime security domain, the thesis claims that the European Union is a sea power from the perspective of modern sea power theory. Sea power theory is a branch of geopolitical theory. Modern sea power theory is based on the widest interpretation of the concept of sea power, arguing that sea power includes not only a military element but also geographical, economic, political, and strategic considerations, and possesses three functions: to protect maritime shipping, to maintain control of the sea and to influence events on land by naval means. Sea power has inputs and outputs.

Through the lens of sea power theory, the thesis analyses the different elements of European Union sea power, explores how this is generated and carries out a thorough investigation of its practice through four detailed case studies, including three maritime Common Security and Defence Policy missions ‒ Operation Atalanta, Operation Sophia and Operation IRINI ‒ EU-funded Critical Maritime Routes programmes and the planned Coordinated Maritime Presences in the Gulf of Guinea, as well as the practice of ‘soft sea power’ in the South China Sea. Ultimately, the thesis presents the findings that the generation of European Union sea power is the consequence of the integration procedure as well as the demands of globalisation, and that this is a regional sea power with limited military strength, focusing on the fight against non-traditional maritime threats in addition to the maintenance of good order at sea.