This article is about the generic foreign affairs term. See The National Interest for the political journal.

The national interest, often referred to by the French term raison d'état, is a country's goals and ambitions whether economic, military, or cultural. The notion is an important one in international relations where pursuit of the national interest is the foundation of the realist school.

The national interest of a state is multi faceted. Primary is the state's survival and security. Also important is the pursuit of wealth and economic growth and power. Many states, especially in modern times, regard the preservation of the nation's culture as of great importance.

In early human history the national interest was usually viewed as secondary to that of religion or morality. To engage in a war rulers needed to justify the action in these contexts. The first thinker to advocate for the primacy of the national interest is usually considered to be Niccolo Machiavelli. The practice is first seen as being employed by France in the Thirty Years War when it intervened on the Protestant side, despite its own Catholicism, to block the increasing power of the Holy Roman Empire. The notion of the national interest soon came to dominate European politics that became fiercely competitive over the next centuries. States could now openly embark on wars purely out of self-interest. Mercantilism can be seen as the economic justification of the aggressive pursuit of the nation interest. The policy of having a foreign policy geared towards pursuing the national interest is the foundation of the realist school of international relations.

The realist school reached its greatest heights at the Congress of Vienna with the practice of the balance of powers, which amounted to balancing the national interest of several great and lesser powers. Metternich was celebrated as the principal artist and theoretician of this balancing but he was simply doing a more or less clean copy of what is predecessor Kaunitz had already done by reversing so many of the traditional Habsburg alliances and building international relations anew on the basis of national interest instead of religion or tradition.

These notions became much criticized after the bloody debacles of the First and Second World Wars. New schools of international relations were developed stressing multilateralism. Mercantilism, which had earlier been discarded, was replaced with a focus on free trade and economic cooperation. Many consider these liberal international systems to have had limited successes and the realist school still has many adherents. Perhaps most notable is the former U.S. Secretary of State Henry Kissinger, who was a great fan of Metternnich.