A military secret is secret information that is purposely not made available to the general public by the military in order to gain an advantage, not reveal a weakness, avoid embarrassment, or to help in propaganda efforts.

Most military secrets are military in nature, such as the strengths and weaknesses of weapons systems, tactics, training methods, number and location of specific weapons, and plans.

Some involve information in broader areas, such as secure communications, cryptography, intelligence operations, and cooperation with third-parties.

The phrase "military secret" has been replaced in governmental language by the doublespeak phrase classified information.

See also: Military intelligence, Espionage