The Douglas A-4 Skyhawk is a carrier-capable ground-attack aircraft designed for the United States Navy and United States Marine Corps. The delta winged, single-engined Skyhawk was designed and produced by Douglas Aircraft Company, and later McDonnell Douglas. It was originally designated the A4D under the U.S. Navy's pre-1962 designation system.

The A-4 is a compact, light-weight design with a maximum takeoff weight of 24,500 pounds (11,100 kg) and has a top speed of more than 600 miles per hour (970 km/h). The aircraft's five hardpoints support a variety of missiles, bombs and other munitions and was capable of delivering nuclear weapons using a low altitude bombing system and a "loft" delivery technique. Prior to the A-4E, power was supplied by the Wright J65; with the A-4E, the installed engine became the 9,300-pound-force (41 kN) Pratt & Whitney J52.

Skyhawks played key roles in the Vietnam War, the Yom Kippur War, and the Falklands War. Fifty years after the aircraft's first flight, some of the nearly 3,000 produced remain in service with several air arms around the world, including 12 A-4(9 A-4KU and 3 TA-4KU) that have been modernized (and are scheduled to operate up to 2025) for the Brazilian Navy's aircraft carrier, São Paulo.

A4, A04, A.IV, A.4 or A-4 may refer to: