The book addresses the most pertinent theoretical and practical issues affecting the broad topic of harmonisation in the fields of environmental and energy law in a comprehensive and critical manner. In this respect, it constitutes a timely and meaningful contribution to the ongoing debate on the conceptual underpinnings, legal techniques and sector-specific problems concerned, while enriching the debate and promoting a more enhanced, coordinated regime to tackle environmental and energy issues in the European Union. Environmental legislation is often incoherent and fragmented, creating hurdles to its effective application. Consequently, rule makers need to resort to harmonisation, which is seen as referring to a number of techniques and instruments that all aim to clarify rules and establish a more coherent and solid legal framework. The book examines the merits of this approach within the context of the European Green Deal and the increasing urgency of the environmental and climate crisis, as well as the obstacles encountered and the questions arising from these complex processes. By bringing together more than fifteen renowned experts in the fields of European environmental and energy law, this book aims to dissect the most critical aspects of and obstacles in the process of strengthening coordination and, ultimately, effectiveness of the existing legal regimes in the field of environmental and energy law in the European Union while sparking further research in the field. Harmonisation in EU Environmental and Energy Law is highly recommended reading for legal scholars specialising in European environmental and energy law, as well as practitioners working in these fields.