The Northrop Grumman MQ-8 Fire Scout is an unmanned autonomous helicopter developed by Northrop Grumman for use by the United States Armed Forces. The Fire Scout is designed to provide reconnaissance, situational awareness, aerial fire support and precision targeting support for ground, air and sea forces. The initial RQ-8A version was based on the Schweizer 330, while the enhanced MQ-8B was derived from the Schweizer 333. The larger MQ-8C Fire Scout variant is based on the Bell 407.

In February 2018, 23 MQ-8Bs were in service with the U.S. Navy. The MQ-8B was retired from service in October 2022.

As the US Navy was withdrawing its RQ-2 Pioneers from service, it began to seek a second generation UAV. The Navy requirement specified a vertical takeoff & landing (VTOL) aircraft, with a payload capacity of 90 kg (200 lb), a range of 125 miles (200 km), an endurance on station of three hours at an altitude of 20,000 feet (6,100 m), and the ability to land on a ship in a 29 mph (47 km/h; 13 m/s) wind. The UAV was to fly 190 hours before planned maintenance.

There were three finalists in the competition, which was designated "VTOL-UAV" or "VTUAV". Bell, Sikorsky, and a collaboration of Teledyne Ryan and Schweizer Aircraft submitted designs. The Ryan-Schweizer UAV was selected as the winner in the spring of 2000. The RQ-8A Fire Scout, as it was named, was a derivative of the Schweizer three-passenger, turbine powered 330SP helicopter, with a new fuselage, new fuel system, and UAV electronics and sensors.

The initial prototype of the Fire Scout was piloted in initial tests, flying autonomously for the first time in January 2000. The Rolls-Royce 250-C20 turbine engine ran on JP-8 and JP-5 jet fuel (the latter of which has a higher flashpoint and is considered safe for shipboard storage and use).

The Fire Scout was to be fitted with a sensor ball turret that carries electro-optic and infrared cameras, and a laser range finder. It was to be controlled over a data link derived from the Northrop Grumman RQ-4 Global Hawk UAV, operating over a line of sight to a distance of 172 miles (280 km). The control system was to be fitted onto a ship, or could be carried on a Humvee light vehicle for US Marine service.

Although progress on the project had been regarded as satisfactory, the Navy decided the Fire Scout didn't meet their needs after all, and cut funding for production in December 2001. However, the development program continued, and Northrop Grumman pitched a range of improved configurations to anyone who was interested. As it turned out, the U.S. Army was very interested, awarding a contract for seven improved RQ-8B evaluation machines in late 2003. In 2006, it was redesignated MQ-8B.

The MQ-8B features a four-blade main rotor, in contrast to the larger-diameter three-blade rotor of the RQ-8A, to reduce noise and improve lift capacity and performance. The four-blade rotor had already been evaluated on Fire Scout prototypes. They increase gross takeoff weight by 500 pounds (230 kg), to 3,150 pounds (1,430 kg) with payloads of up to 700 pounds (320 kg) for short-range missions. The MQ-8B is 23.95 feet (7.30 m) long, 6.2 feet (1.9 m) wide, and 9.71 feet (2.96 m) tall.