This chapter introduces the role of the National Regulatory Authorities in European market coupling in line with the Electricity Directive (EU) 2019/944. National Regulatory Authorities are assigned a crucial role to adopt and enforce the market coupling mechanisms in Europe. These tasks and duties are assigned to them by the legislative energy package in Europe, against the background of the electricity market liberalization process. This chapter highlights some key challenges which may need to be addressed to truly deliver on a harmonized, transparent, and efficient European Internal Electricity Market: national interests, institutional and governance barriers, enforcement mechanisms and information asymmetry. Where these aspects are not dealt with properly, suboptimal market design choices risk being implemented.