ArmaLite, or Armalite, is an American small arms engineering company, formed in the early 1950s in Hollywood, California. Many of its products, as conceived by chief designer Eugene Stoner, relied on unique foam-filled fiberglass butt/stock furniture and a composite barrel using a steel liner inside an aluminum sleeve, including the iconic AR-15/M16 family. While the original ArmaLite ceased doing business in the 1980s, the brand was revived in 1996, by Mark Westrom.

Originating as the light firearms division of Fairchild Engine and Airplane Corporation, ArmaLite was formally incorporated in 1954. Stoner's first design, the AR-1 Parasniper (dating from 1952), was relatively unsuccessful. However, in 1956, when ArmaLite competed in a contest for an aircrew survival rifle, its AR-5 and AR-7 designs were put into production and adopted by elements of the US military. In 1957, ArmaLite also competed for the contract for a new main US combat rifle, in the NATO standard 7.62 mm caliber, with its AR-10. While that bid was unsuccessful, the rifle attracted the attention of both Colt and the Dutch company Artillerie-Inrichtingen, both of which acquired licenses to manufacture the AR-10.

In 1962, Fairchild relinquished its interest in ArmaLite, which continued as an independent company.

The AR-15, chambered for the new, lightweight, high velocity 5.56 mm round, included features of Stoner's previous designs. Under financial pressure, ArmaLite sold the entire rights to the AR-15 design to Colt, which quickly secured significant US military and law enforcement contracts for the weapon, beginning with the USAF Security Forces (1962). A variant of the Colt product was adopted as the US Army's main combat rifle, from 1964, as the Rifle, Caliber 5.56 mm, M16. By the 1980s, it had also been adopted by the militaries of many US allies, especially within NATO countries. The M16 remained the primary combat rifle of the US military until 2016. Furthermore, its replacements have often been derivatives of the M16 (e.g. the M4 carbine), or other ArmaLite and/or Eugene Stoner designs (e.g. M27–IAR).

ArmaLite had other brushes with success, especially with the AR-18 (also 5.56 mm). They were not enough to sustain the company and it ceased operations in the early 1980s. The design rights and name were purchased in 1996 by Mark Westrom, who re-launched the company ArmaLite, Inc., headquartered in Geneseo, Illinois northwest of Peoria. In 2013, Westrom sold ArmaLite, Inc. to Strategic Armory Corps, which owns AWC Silencers, Surgeon Rifles, Nexus Ammo, and McMillan Firearms. SAC was formed to acquire and combine market-leading companies within the firearms industry. In 2014, 3-gun champion Tommy Thacker was appointed president. In 2015, ArmaLite introduced 18 new products, including the AR-10 and the M-15 platform firearms. In mid-2018, ArmaLite moved to Phoenix. As of mid-2023 Strategic Armory Corps and its subsidiaries (including Armalite) relocated headquarters to be based out of Bryan/College Station, Texas.

ArmaLite began as a small arms engineering concern founded by George Sullivan, the patent counsel for Lockheed Corporation and funded by Fairchild Engine and Airplane Corporation. After leasing a small machine shop at 6567 Santa Monica Boulevard in Hollywood, Sullivan hired several employees and began work on a prototype for a lightweight survival rifle for use by downed aircrew. On October 1, 1954, the company was incorporated as the ArmaLite Corporation, becoming a subsidiary of Fairchild. With its limited capital and tiny machine shop, ArmaLite was never intended to be an arms manufacturer but instead was focused on producing small arms concepts and designs to be sold or licensed to other manufacturers. While testing the prototype of ArmaLite's survival rifle design at a local shooting range, Sullivan met Eugene Stoner, a talented small arms inventor, whom Sullivan immediately hired to be ArmaLite's chief design engineer. Stoner was a US Marine in World War II and an expert with small arms. Since the early 1950s, he had worked various jobs while building gun prototypes in his spare time. At the time, ArmaLite Inc. was a small organization. As late as 1956, it had only nine employees, including Stoner.

With Stoner as the chief design engineer, ArmaLite quickly released several innovative rifle ideas. The first ArmaLite concept to be adopted for production was the AR-5, a survival rifle chambered for the .22 Hornet cartridge. The AR-5 was adopted by the U.S. Air Force as the MA-1 Survival Rifle.

A civilian survival weapon, the AR-7, was later introduced and chambered in .22 long rifle. The semi-automatic AR-7, like the AR-5, could be disassembled and the components stored in the buttstock. Primarily made of alloys, the AR-7 floats, whether assembled or stored, due to the design of the buttstock which is filled with plastic foam. Several companies have produced the AR-7 and derivative models since their introduction in the late 1950s, including Henry Repeating Arms, of Bayonne, New Jersey on the Bergen Neck peninsula east of Elizabeth.