The Agusta A129 Mangusta (English: Mongoose) is an attack helicopter originally designed and produced by Italian company Agusta. It is the first attack helicopter to be designed and produced wholly in Europe. It has continued to be developed by AgustaWestland, the successor company to Agusta. It has been exclusively operated by the Italian Army, which introduced the type to service during 1990.

The A129 has undergone several combat deployments, seeing use in Somalia, Afghanistan, and Iraq. It has proven well suited to operating in hot climates, as well as quite flexible in the field. The original 60 rotorcraft have been upgraded multiple times since entering service with the Italian Army; improvements have included compatibility with additional munitions, new targeting systems, improved avionics, better data-handling, and a more powerful transmission. Various improvements and export models have been proposed, including dedicated naval and reconnaissance variants. The TAI/AgustaWestland T129 ATAK derivative has been developed by Turkish Aerospace Industries in cooperation with AgustaWestland for the Turkish Army as well as other services and export customers. Since 2017, work has been underway on a larger successor to the A129 for the Italian Army, the Leonardo Helicopters AW249.

In 1972, the Italian Army began forming a requirement for a light observation and anti-tank helicopter; one prominent factor in shaping this requirement was the need to address the threat posed by the extensive military assets in operation with the Warsaw Pact countries and those of the Soviet Union. Around the same time as the Italian efforts were underway, the West German military had also identified a similar need. The two nations' parallel requirements ultimately led to a joint project being initiated between the Italian company Agusta and West German company MBB; however, this cooperative effort did not last long, and was dissolved shortly after preliminary work had been undertaken. Agusta had initially studied the development of a combat-oriented derivative of its existing A109 helicopter, however the company decided to proceed with the development of a more ambitious helicopter design.

In 1978, Agusta formally began the design process on what would become the A129. On 11 September 1983, the first of five A129 prototypes made the type's maiden flight; the fifth prototype would first fly in March 1986. Around the same time, the Italian Army placed an order for a total of 60 A129s. At one stage, a total of 100 attack helicopters had been planned to be purchased but this was slashed to 60 A129s. Another version of the type was to be capable of hauling eight troops in addition to its firepower capabilities; this variant, referred to sometimes as the A139, never got off the ground. According to defence publication Jane's Information Group, by 1985, the A129 was considered to be a comparable attack helicopter to the American-built McDonnell Douglas AH-64 Apache, and showed potential on the export market.

During the 1980s, Agusta sought to partner with Westland Helicopters to develop a common light attack helicopter, other prospective manufacturing participants in the joint initiative included Fokker and Construcciones Aeronáuticas SA. In 1986, the governments of Italy, the Netherlands, Spain and the United Kingdom signed a memorandum of understanding to investigate an improved version of the A129, alternatively called the Joint European Helicopter Tonal or Light Attack Helicopter (LAH). By 1988, feasibility studies for four different options had been conducted for the LAH, these would have between 80 per cent and 20 per cent growth over the initial A129; both single-engine and twin-engine configurations were examined using various new powerplants, as well as a new rotor system, retractable landing gear, improved sensors and more powerful armament. However, the LAH project collapsed in 1990 following Britain and the Netherlands independently deciding to withdraw from the program and eventually procure the AH-64 Apache instead.

Agusta retained its interest in pursuing export sales and decided to proceed with the development of the A129 International, or A129I; this was a dedicated and upgraded version of the A129 intended for export customers. The A129I featured a five-bladed main rotor (early production aircraft had employed a four-bladed main rotor), a pair of LHTEC T800 engines (replacing the Rolls-Royce Gem engines of Italian Army Mangustas) and an upgraded transmission; the A129I were also provisioned with new weapons and electronic warfare systems. In 1998, the Italian Army had decided to upgrade a portion of their A129 fleet with many of the A129I's systems, the first of the remanufactured helicopters was delivered in 2002. In September 2007, the A129I was formally redesignated as the AW129.

During the Australian Army's AIR 87 project to procure a new Armed Reconnaissance Helicopter fleet, the Agusta A129 was one of the contenders; it was one of the three attack helicopters, alongside the AH-64 Apache and the Eurocopter Tiger, to be short-listed out of the six tenders submitted. In December 2001, Australia announced its selection of the Eurocopter Tiger as the winning bid.

Turkey had sought a new attack helicopter since the 1990s to replace their diminished Bell AH-1 Cobra and Bell AH-1 SuperCobra fleets. Following a highly protracted selection process, in September 2007, an order was issued for 51 TAI/AgustaWestland T129 ATAK helicopters, a variant of the A129 International. As a part of the deal with AgustaWestland, Turkish defense firm TAI acquired the rights for future manufacturing of the T129; in addition to production for local purposes, TAI also manufacture the T129 for export customers. Various components and avionics systems are intended to be replaced with indigenously produced systems as they are developed.