This book provides a comprehensive analysis of the regulatory challenges and legal barriers surrounding the MaaS concept in the EU. By evaluating MaaS against existing EU legal frameworks on data sharing, competition, transport law and beyond, this research seeks to shed light on the regulatory implications of the MaaS concept. It employs a problem-based approach and qualitative doctrinal legal research methodology to assess the potential of MaaS in enhancing the efficiency, accessibility, sustainability, digitalization, multimodality, competitiveness, and convenience of the EU passenger transport sector, while identifying shortcomings in current EU regulatory frameworks that may impede its growth and analysing potential harms that rise of MaaS might cause to competition and users. The book concludes by providing recommendations aimed at enhancing the EU legal frameworks, with the goal of establishing a unified and harmonized framework that promotes an open, competitive, and multimodal MaaS market. In summary, producing a book on the regulatory challenges of MaaS in the EU now can contribute to the ongoing discourse, provide valuable insights, and offer guidance for policymakers, regulators, industry stakeholders, and researchers involved in shaping the future of mobility.