The Northrop YB-49 was a prototype jet-powered Flying Wing heavy bomber aircraft developed by Northrop for the United States Air Force shortly after World War II. It was the jet development of the piston-engined Northrop XB-35 and YB-35 Flying Wing, and the two YB-49s actually built were both converted YB-35 test aircraft. The jet-powered Flying Wing never entered production, being passed over in favor of the more conventional but obsolete Convair B-36 Peacemaker propeller-driven design. Design work performed in the development of the YB-35 and YB-49, nonetheless proved to be valuable to Northrop in the eventual development of the current day B-2 strategic bomber which first entered operational service in the 1990s.

One YRB-49A had been completed when, in September 1948, the Air Force ordered the type into full production as the RB-49A reconnaissance aircraft. It was powered by six jet engines, two of them externally mounted in under wing pods, ruining the Flying Wing's sleek, aerodynamic lines, but extending its recon range with the additional fuel carried.

During early 1950, the remaining YB-35Bs airframes being converted to YRB-49As were scrapped. Flight testing of the sole remaining YB-49 prototype ended 14 March 1950. On 15 March 1950, that program was cancelled, and coincidentally, that last YB-49 prototype suffered a high-speed taxiing accident and, as previously noted, was totally destroyed in the ensuing fire.
But only two months later, all Flying Wing contracts were cancelled abruptly without explanation by order of Stuart Symington, Secretary of the Air Force. Shortly thereafter, Symington also turned down a request from the Smithsonian for the Air Force to donate one of these big wings to its collection of pioneering Northrop aircraft designs.

Northrop's entire Flying Wing program may have been terminated due to its technical difficulties and the program being behind schedule and over budget. Another possible contributing factor to the program's cancellation may have been the tendency of Northrop to become engaged in many experimental programs, which spread its small engineering staff far too wide. While the competing propeller-driven Convair B-36 "Peacemaker" was an obsolete World War II design by this time, and had been having just as many or even more development problems, the Air Force seemed to have greater confidence that its more conventional design and "teething" problems could be overcome, when compared to those of the radical Flying Wing. This conclusion effectively doomed the jet powered Flying Wing program.