This thesis examines the multifaceted nature of energy security within the European Union, with a particular focus on the strategic dynamics of the Southeastern Mediterranean. Moving beyond the narrow definition of energy security as the stable and affordable supply of energy, the study adopts a broader perspective that incorporates geopolitical tensions, technological advancements, and environmental sustainability challenges. As the EU remains heavily dependent on energy imports, especially natural gas, diversification of supply sources and routes has become a key policy priority. In this context, the Southeastern Mediterranean emerges as a critical region, with countries such as Israel, Egypt, and Cyprus discovering substantial offshore gas reserves that offer the EU alternative sources capable of reducing reliance on Russian gas. These developments carry not only economic but also geopolitical implications, reshaping alliances and energy diplomacy in the region. The trilateral cooperation between Greece, Israel, and Cyprus, supported by the United States, exemplifies this strategic shift. Nevertheless, the region also faces significant challenges, including political instability in the aftermath of the Arab Spring, the pressing need for infrastructure investment, and the establishment of coherent legal frameworks for energy cooperation. The thesis argues that the EU’s energy security can only be achieved through coordinated strategies in which the Southeastern Mediterranean plays a central role as an emerging energy hub.