Which came first AR15 or M16 rifle?

The AR-15 rifle was developed first, designed by Eugene Stoner in the late 1950s for the ArmaLite Corporation. It was introduced in 1956, while the M16 rifle, which is a military adaptation of the AR-15, was adopted by the U.S. military in 1964 during the Vietnam War. Thus, the AR-15 predates the M16 by several years.