The BAE Systems Hawk is a British single-engine, subsonic, jet-powered advanced trainer aircraft. Its aluminium alloy fuselage is of conventional string-frame construction. It was first known as the Hawker Siddeley Hawk, and subsequently produced by its successor companies, British Aerospace and BAE Systems. It has been used in a training capacity and as a low-cost combat aircraft.

Operators of the Hawk include the Royal Air Force (notably the Red Arrows display team) and several foreign military operators. The Hawk was produced at BAE Brough until 2020 in the UK, and continues to be produced under licence in India by Hindustan Aeronautics Limited (HAL), with over 1000 Hawks sold to 18 operators around the world.

In 1964, the Royal Air Force specified a requirement (Air Staff Target, AST, 362) for a new fast jet trainer to replace the Folland Gnat. The SEPECAT Jaguar was originally intended for this role, but it was soon realised that it would be too complex an aircraft for fast jet training and only a small number of two-seat versions were purchased. Accordingly, in 1968, Hawker Siddeley Aviation (HSA) began studies for a simpler aircraft, initially as special project (SP) 117. The design team was led by Ralph Hooper.

This project was funded by the company as a private venture, in anticipation of possible RAF interest. The design was conceived of as having tandem seating and a combat capability in addition to training, as it was felt the latter would improve export sales potential. By the end of the year HSA had submitted a proposal to the Ministry of Defence based on the design concept, and in early 1970 the RAF issued Air Staff Target (AST) 397 which formalised the requirement for new trainers of this type. The RAF selected the HS.1182 for their requirement on 1 October 1971 and the principal contract, for 175 aircraft, was signed in March 1972.

The prototype aircraft XX154 first flew on 21 August 1974 from Dunsfold piloted by Duncan Simpson, Chief Test Pilot of HSA (Kingston), reaching 20,000 ft in a flight lasting 53 minutes. All development aircraft were built on production jigs; the program remained on time and to budget throughout. The Hawk T1 entered RAF service in late 1976. The first export Hawk 50 flew on 17 May 1976. This variant had been specifically designed for the dual role of lightweight fighter and advanced trainer; it had a greater weapons capacity than the T.1.

More variants of the Hawk followed, and common improvements to the base design typically included increased range, more powerful engines, redesigned wing and undercarriage, the addition of radar and forward-looking infrared, GPS navigation, and night-vision compatibility. Later models were manufactured with a great variety in terms of avionics fittings and system compatibility to suit the individual customer nation; cockpit functionality was often rearranged and programmed to be common to an operator's main fighter fleet to increase the Hawk's training value.

In 1981, a derivative of the Hawk was selected by the United States Navy as their new trainer aircraft. Designated the McDonnell Douglas T-45 Goshawk, the design was adapted to naval service and strengthened to withstand operating directly from the decks of carriers, in addition to typical land-based duties. This T-45 entered service in 1994; initial aircraft had analogue cockpits, while later deliveries featured a digital glass cockpit. All airframes were planned to undergo avionics upgrades to a common standard.

A major competitor to the Hawk for export sales has been the Dassault/Dornier Alpha Jet; aviation expert John W. R. Taylor commented: "What Europe must avoid is the kind of wasteful competition that has the Hawker Siddeley Hawk and Dassault-Breguet/Dornier Alpha Jet battling against each other in the world market." By early 1998, a total of 734 Hawks had been sold, more than 550 of which had been sold to export customers. Military customers often procured the Hawk as a replacement for older aircraft such as the BAC Strikemaster, Hawker Hunter, and Douglas A-4 Skyhawk.