The present Thesis is taking place in the context of Post-Graduation Program Energy: Strategic, Law & Economics of University of Piraeus - Department of International & European Studies. Its topic is “Competition and Energy - Issues, arising from the Abusive Exploitation of a Dominant Position In the Energy Market”. As it emerges through its title, this Thesis is substantially divided into two parts. The first one, operates a general theoretical view over the relationship between Competition and Energy, with emphasis to the way that Competition’s Policy has shaped Energy policy, at European and National Level, while the second one, turns the Thesis’s approach to specified legal and technical issues, as it seeks to approach the implementation framework of one of the primary enforcement tool of Competition's Policy, which is none other than the Article 102 of TFEU. In particular, the relevant analysis, initiates with an introduction to Energy and its importance as a common good at social, political and economic level and moves forward, demonstrating the development and evolution of the E.U.’s Energy Policy and the Regulations of the Market, as well as the role of Competition Policy as a Driver for the Energy Policy Development, during the period from 1998 until today. This route takes place hilightening the main turning points in energy field - such as liberalization of the energy markets, energy transition and of course the energy crisis after the Russian-Ukraine war. In continuation of the above, the present Thesis deals exclusively with issues of enforcement Competition’s Policy and especially with the Article 102 of TFUE, which prohibits the abuse of dominant position in internal markets. The first step is going through a legal and theoretical approach of the Article 102 and the general categorization of conducts of abuses, while the second step applies the article 102, specifically in Energy Markets, demonstrating the relevant friction points, conducts of abuse, emerging Trends and of course the respective Case Law, which imprint the specificities and needs of these markets. In the above context, the present Thesis concludes, seeking to address the case of Greece and specifically the general view of its Institutional Response to Energy Market Liberalization (1998 - 2025), indicating relevant structural reforms and significant Case Law, that reflect a big part of developments and correlations at energy field in our country.