The aim of this Thesis is to consider a methodological framework suitable to support a primary and primitive investigation and evaluation of the technical applicability and energy feasibility of a specific Energy Island model in Greece. For such purpose, the general concept and the potential applications of Energy Island are presented, and the present situation of the Greek energy sector and RES technologies in Greece are outlined. In order to attempt to evaluate the technical performance of a specific Energy Island model in Greece, a theoretical and hypothetical Multi-Criteria Decision Analysis (MCDA) process is developed and conducted. The methodological framework developed and applied for the present case study pertains to a theoretical decision-making process for the selection of the optimum Energy Island scenario in Greece amongst four (4) alternatives. As derived from the extracted results of the applied MCDA model, the hypothetical scenario with the highest annual energy production and the least environmental and technological issues ranks optimal for all the implicated stakeholders and is considered the most preferred alternative. This Thesis concludes that the perspective of the various applications of the concept of the Energy Island model has the potential to contribute to more efficient utilization of the available RES technologies in Greece, in order to accelerate the decarbonization of the Greek energy system as well as to assure the security of the system, by replacing the existing conventional fossil fuel generation plants with clean offshore renewable energy.