Who developed the M16/AR15 weapon system?

Eugene Stoner developed the M16/AR15 weapon system.

Stoner was an American firearms designer who worked for the ArmaLite division of Fairchild Engine and Airplane Corporation. In the late 1950s, he developed the lightweight AR-15 rifle from the earlier AR-10 design. The AR-15 used a small-calibre, high-velocity cartridge and extensive aluminium construction, making it substantially lighter than many earlier military rifles.

The U.S. military adopted a modified version of the AR-15 as the M16. The rifle entered service during the Vietnam era, where its performance and maintenance generated controversy before later improvements addressed many early problems. The M16 family subsequently became one of the world’s best-known military rifle systems.

The answer is sometimes complicated by credit given to other ArmaLite engineers, including Jim Sullivan and Bob Fremont, who contributed to the design and development process. However, Eugene Stoner is the canonical answer to who developed the AR-15 and its military M16 evolution.