The small but sleek Aérospatiale AS 350 Écureuil (Squirrel) was one of two designs (the other being the much larger Dauphin 2) built to succeed the venerable Alouette III in a wide variety of military and civil roles emphazising good fuel economy and low maintenance costs. The Écureuil is a small but sleek-looking utility helicopter of conventional design, initially powered by a single turboshaft engine but later adopting a twin-engine configuration to drive the three-blade rotor. A number of these were adopted for military purposes but eventually, a dedicated military version was designed as the AS 550 Fennec (Desert Fox) which comes in both land-based and naval versions, advanced avionics, and the ability to carry a wide array of weaponry including guns, rockets, torpedoes, and missiles. Both Écureuil and Fennec helicopters have been adopted by large number of foreign operators ammounting to well over 20 nations (including license production in Brazil by Helibras) using them for military and police duties.

The first prototype of the Écureuil had its maiden flight on 27 June 1974, entering service as the AS 350B (known as the AStar in North America). Development eventually diverged into single and twin-engined versions, the latter designated as the AS 355E Écureuil 2 (Twin Star in North America). Later improvements led to the AS 350B1/B2/B3 with upgraded powerplants and the AS 355F with a new aerofoil section and increased payload. The first purpose-built military versions were the AS 350L and AS 355M which were redesignated AS 550C3 and AS 555N (with single and twin engines respectively) and renamed Fennec. Among these, the AS 555 UN and AS 555AN are land-based types specializing in reconnaissance and observation with the latter version being armed. Naval variants are the AS 555MN and AS 555SN, the first of which performs surveillance missions while the later is optimized for anti-submarine warfare and can be armed with a torpedo. More recent developments include the single-engine EC 130B4 which features a Fenestron tail and enlarged cabin, while in RAF service the Écureuil is known as the Twin Squirrel HCC.1, based on the AS 335N with FADAC engine systems.