A national security council (NSC) is usually an executive branch governmental body responsible for coordinating policy on national security issues and advising chief executives on matters related to national security. An NSC is often headed by a national security advisor and staffed with senior-level officials from military, diplomatic, intelligence, law enforcement and other governmental bodies. The functions and responsibilities of an NSC at the strategic state level are different from those of the United Nations Security Council, which is more of a diplomatic forum.

Occasionally a nation will be ruled by a similarly named body, such as "the National Security Committee" or "Council for National Security". These bodies are often a result of the establishment or preservation of a military dictatorship (or some other national crisis), do not always have statutory approval, and are usually intended to have transitory or provisional powers. See also: coup d'état.

Some nations may have a similar body which is not formally part of the executive government. For example, the National Security Commission in China is an organ of the Chinese Communist Party (CCP), the sole ruling party, and headed by the CCP general secretary, rather than an organ of the executive government.