Majestic-12 or Majic 12 (sometimes written simply as MJ-12 or MJ-XII) is the code name of a secret committee of high-level scientists, military leaders, and government officials, formed in 1947 at the direction of U.S. President Harry S. Truman. The purpose was to investigate UFO activity. This committee is an important part of an ongoing government exploitation and cover up of UFO information. MAJIC is the security classification for all information about "actual" UFOs and aliens. The code names of the various component projects under Majestic-12 change from time to time; the creation of the Department of Homeland Security in 2003 is partially the result of changes in the Majestic-12 structure.

Majestic-12 first entered the public consciousness in 1984, in a 1982 made-for-television documentary, The UFO Experience. The existence of MJ-12 has been denied by the United States government, which insists that documents suggesting its existence are hoaxed. A disturbingly, or amusingly, large amount of unconfirmed information about Majestic-12 is available to the public; much of this information is contradictory or ridiculous, and may be deliberate disinformation.

According to "fringe" conspiracy theorists, Majestic-12 is coordinating alien contact with Earth, as well as the operations towards a New World Order. Under this direction, MJ-12 has far-reaching powers, and are responsible for all scientific operations at Area 51, Dulce, New Mexico, and the Frenchman's Mountain installations. Groups such as the Trilateral Commission, the Masons, the Bilderbergers, the Communist Party, the Council on Foriegn Relations, the Rand Corporation, the international narcotics trade, etc. have been tied to the Majestic-12 conspiracy at one time or another. In this view, Majestic-12 is entirely a malign influence, whose leaders (if still human) have no concern for law, human rights, or conventional morality.

According to less extravagant conspiracy theory lore, Majestic-12 was created with a more humble goal: to cover up alien activities on Earth, and liaise with the aliens to obtain technology in exchange for knowledge and testing on human biology. If this is the case, the Majestic-12 committee may see themselves as defenders of the United States.

Delta Green has no knowledge of any organizations analogous to Majestic-12 in foreign countries (although of course they would be extremely secretive). Reports of UFOs and flying saucers certainly occur in all parts of the Earth.

In either case, Majestic-12 controls secret research and development laboratories where advanced devices are created using alien knowledge. Recovery teams exist to obtain (or destroy) any evidence of alien presence, and to discredit public reports about such evidence. The Majestic-12 committee has apparently unlimited power and authority within the Federal government; the legality of this power and authority is impossible to determine. It is certainly possible that Majestic-12 is operating with no more "legality" than Delta Green. The amount of information regarding the Menace held by Majestic-12 is unknown.

Administration and central records for the Majestic-12 committee were at one time located in a facility known informally as "the Country Club", in Maryland. This facility is thought to have been superseded by a more secure meeting location or process, after the public disclosures regarding Majestic-12 in the mid-eighties.