Needing to replace the elderly A-1 Skyraider piston-engined attack plane that dated back to the end of World War II, the US Navy instigated a competition to develop a day/night, all-weather, long-range, low-level, jet-powered attack aircraft. After reviewing eleven designs from eight manufacturers, Grumman's G-128 was selected the winner in 1957, and the company preceeded to develop the A2F-1 (later redesignated A-6A) for both the Navy and Marine Corps.

Unlike most planes of the era designed for supersonic flight and high performance, the A-6 sacrificed speed and maneuverability for exceptional bombing accuracy and payload. The rather conventional design featured a mid-mounted swept wing equipped with full-span slats along the leading edge and nearly full-span single-slotted flaps along the trailing edge. Instead of ailerons, the A-6 wing employed large spoilers located just ahead of the flaps to provide roll control when deflected differentially and to act as lift dumpers when deflected together while the wingtips split open to act as airbrakes.

The bulbous fuselage provided space for a large attack radar, side-by-side seating under the cockpit canopy, two J52 turbojets fed by large cheek inlets, and a sophisticated array of electronic countermeasures and threat receivers. Despite early development troubles, the A-6 emerged as a superb attack aircraft in Vietnam where its advanced avionics suite, heavy payload, large fuel capacity, and sturdy construction made the Intruder one of the most durable and versatile planes in the theater.

The most successful variant was the A-6E equipped with a powerful multi-mode tracking and terrain-following radar and equipped to carry laser-guided bombs. The TRAM upgrade program saw the installation of the Hughes Target Recognition and Attack, Multisensor turret located under the nose and containing a Forward Looking Infrared (FLIR), laser designator, and laser receiver. Further upgrades throughout the 1980s and 1990s allowed the A-6 to carry the latest array of precision guided munitions. Several A-6Es were also fitted with improved cockpit lighting systems compatible with night vision goggles enabling pilots to reduce the low-level cruising altitude from 500 ft (150 m) to 200 ft (60 m) at night.

Although the Navy had shown interest in an upgraded A-6F equipped with even more capable avionics and a new radar, the program was cancelled following the decision to build the A-12 Avenger. Grumman's later attempt to develop a cheaper A-6G also failed, but the Navy did pursue a series of structural and avionics upgrades to extend the service life of the A-6E into the mid-1990s. Nevertheless, both the Navy and Marine Corps A-6 fleets were withdrawn following the Gulf War with the final front-line squadron retired in 1997. The duties of the A-6 were split between the F/A-18 attack fighter, upgraded models of the F-14 equipped with precision bombing capability, and the S-3, none of which could replace the range, payload or tanking capabilities of the Intruder.