The United States Northern Command (USNORTHCOM) is one of eleven unified combatant commands of the United States Department of Defense. The command is tasked with providing military support for non-military authorities in the U.S., and protecting the territory and national interests of the United States within the continental United States, Puerto Rico, Canada, Mexico, The Bahamas, and the air, land and sea approaches to these areas. It is the U.S. military command which, if applicable, would be the primary defender against an invasion of the U.S.

A unified combatant command, also referred to as a combatant command (CCMD), is a joint military command of the United States Department of Defense that is composed of units from two or more service branches of the United States Armed Forces, and conducts broad and continuing missions. There are currently 11 unified combatant commands, and each is established as the highest echelon of military commands, in order to provide effective command and control of all U.S. military forces, regardless of branch of service, during peace or during war time. Unified combatant commands are organized either on a geographical basis or on a functional basis, e.g., special operations, force projection, transport, and cybersecurity. Currently, seven combatant commands are designated as geographical, and four are designated as functional. Unified combatant commands are "joint" commands and have specific badges denoting their affiliation.