Thanks to technological advancements in recent years, critical infrastructure has become both irreplaceable for modern social life—and highly vulnerable. Safe, effective and efficient management of critical infrastructure is a sign of a state’s social welfare and economic development. Ensuring the security of critical infrastructure is essential for national security, and is becoming ever more dependent on network technology. Indeed, providing for the cybersecurity of critical infrastructure, i.e., protecting it from cyber attack, is the chief goal of modern states’ cybersecurity strategy. The present study aims to reveal the importance of ensuring the cybersecurity of critical infrastructure within the scope of national security. First, the relationship between the concept of national security and cyber threats is scrutinized from a realist perspective. The interaction of the critical infrastructure concept and cybersecurity is then analyzed from a theoretical and technical point of view. In addition to official documents published by the United States, which has the world’s most advanced cybersecurity infrastructure, the study includes definitions of related concepts published by Turkey, a country that has made significant progress in recent years in terms of the cybersecurity of its critical infrastructure.