Unmanned aerial vehicles (UAVs) include both autonomous (capable of operating without human input) drones and remotely piloted vehicles (RPVs). A UAV is capable of controlled, sustained level flight and is powered by a jet, reciprocating, or electric engine. In the twenty-first century, technology reached a point of sophistication that the UAV is now being given a greatly expanded role in many areas of aviation.

A UAV differs from a cruise missile in that a UAV is intended to be recovered after its mission, while a cruise missile impacts its target. A military UAV may carry and fire munitions on board, while a cruise missile is a munition. Loitering munitions are a class of unmanned aircraft intermediate between them.

The earliest recorded use of an unmanned aerial vehicle for warfighting occurred in July 1849, serving as a balloon carrier (the precursor to the aircraft carrier) is the first offensive use of air power in naval aviation. Austrian forces besieging Venice attempted to float some 200 incendiary balloons each carrying a 24- to 30-pound bomb that was to be dropped from the balloon with a time fuse over the besieged city. The balloons were launched mainly from land; however, some were also launched from the Austrian ship SMS Vulcano. The Austrians used smaller pilot balloons to determine the correct fuse settings. At least one bomb fell in the city; however, due to the wind changing after launch, most of the balloons missed their target, and some drifted back over Austrian lines and the launching ship Vulcano.

The first pilotless aircraft were built during World War I. From a suggestion that A. M. Low’s expertise in early television and radio technology be used to develop a remotely controlled pilotless aircraft to attack the Zeppelins a remarkable succession of British drone weapons in 1917 and 1918 evolved. Designers from Sopwith Aviation and its contractor Rushton Proctor, de Havilland and the Royal Aircraft Factory all became involved. They were all designed to use Low's radio control system developed at the Royal Flying Corps secret Experimental Works at Feltham. Of these Low confirmed that Geoffrey de Havilland’s monoplane was the one that flew under control on 21 March 1917. Low is known as '"father of radio guidance systems" and in 1976 Low was inducted into the International Space Hall of Fame. Alternatively, John Taylor suggested Low was the ‘Father of the Remotely Piloted Vehicle’.

Soon after, on September 12, the Hewitt-Sperry Automatic Airplane, otherwise known as the "flying bomb" made its first flight, demonstrating the concept of an unmanned aircraft. They were intended for use as "aerial torpedoes," an early version of today's cruise missiles. Control was achieved using gyroscopes developed by Elmer Sperry of the Sperry Gyroscope Company.

Later, in November 1917, the Automatic Airplane was flown for representatives of the US Army. This led the army to commission a project to build an "aerial torpedo", resulting in the Kettering Bug which first flew in 1918. While the Bug's revolutionary technology was successful, it was not in time to fight in the war, which ended before it could be fully developed and deployed.

After World War I, three Standard E-1s were converted to drones. The Larynx was an early cruise missile in the form of a small monoplane aircraft that could be launched from a warship and flown under autopilot; the Royal Navy tested it between 1927 and 1929. The early successes of pilotless aircraft led to the development of radio controlled pilotless target-aircraft in Britain and the US in the 1930s. In 1931 the British developed the Fairey Queen radio-controlled target from the Fairey IIIF floatplane, building a small batch of three, and in 1935 followed up this experiment by producing larger numbers of another RC target, the "DH.82B Queen Bee", derived from the de Havilland Tiger Moth biplane trainer. The name of "Queen Bee" allegedly led to the use of the term "drone" for pilotless aircraft, particularly when they are radio-controlled. During this period, the U.S. Navy, continuing work that reached back to 1917, also experimented with radio-controlled aircraft. In 1936 the head of US Navy research group used the term "DRONE" to designate radio-controlled aerial targets. From 1929 Hungarian scientist Kálmán Tihanyi worked on television guidance for defense applications, building prototypes of a camera for remotely-guided aircraft in London for the British Air Ministry, and later adapting it for the Italian Navy. In 1929, Tihanyi invented the first infrared-sensitive (night-vision) electronic television-camera for anti-aircraft defense in Britain. The solutions of the technology that Tihanyi depicted in his 1929 patent became so influential that American UAV-producing companies still used many of its solutions even half a century later, until the mid-1980s.

Subsequent British "drones" included the Airspeed Queen Wasp, the Miles Queen Martinet, and the US-supplied Curtiss Queen Seamew. After WW II these would be replaced by the jet-powered Anglo-Australian GAF Jindivik.^{[citation needed]}