M16 rifle, officially designated Rifle, Caliber 5.56 mm, M16, is a family of military rifles adapted from the ArmaLite AR-15 rifle for the United States military.

The original M16 rifle was a 5.56 mm automatic rifle with a 20-round magazine.

M16 originally used by the U.S. Air Force, was equipped with triangular handguards, butt stocks without a compartment for the storage of a cleaning kit, a three-pronged flash suppressor, full auto, and no forward assist. Bolt carriers were originally chrome plated and slick-sided, lacking forward assist notches. Later, the chrome plated carriers were dropped in favor of Army issued notched and parkerized carriers though the interior portion of the bolt carrier is still chrome-lined.

The U.S. Air Force continued to use M16 until 2001, before converted to the M16A2.

M16 entered US military service In 1964 and used for jungle warfare operations during the Vietnam War

British SAS also used M16 during the Falklands War