National cyberspace encompasses a broad range of entities, including private and public sector actors as well as citizens. Cybersecurity is crucial for the fundamental functioning of the national economy, the operation of critical infrastructure, the essential services of society, citizens’ trust in digital services, and national defense. National cyberspace can be categorized into six dimensions: military, political, economic, societal, technological, and citizen. This chapter outlines these dimensions of cyberspace, the cybersecurity threats they encounter, and highlights the regulations implemented by the European Union to bolster cybersecurity in its member states.