Walter and Reimar Horten, German aeronautical engineers whose tailless flying-wing gliders of the 1930s led to the Ho 229, a jet-powered flying wing of which one prototype flew in 1945; the surviving airframe is held by the Smithsonian.
Why they appear in the UFO literature
They are the real German programme the Nazi Flying Disc Legend borrows its plausibility from. The flying wing was genuinely radical, genuinely low-observable by accident of its planform, genuinely captured under Project Lusty, and genuinely years ahead of anything the Allies had flown. That the Reich had exotic airframe work in progress is a documented fact; that it had disc-shaped craft with novel propulsion is a claim with no archive behind it, and The Hunt for Zero Point spends two chapters demolishing the Prague and Breslau saucer stories on exactly that ground.
The brothers themselves went in different directions after the war, Reimar to Argentina and Walter into the postwar German air force, and neither ever claimed anything of the kind the legend attributes to their programme.
Connections
Nazi Flying Disc Legend · Project Lusty · The Hunt for Zero Point · Operation Paperclip · Renato Vesco · Rudolf Lusar · Have Blue