The B&F Fk12 Comet, also called the FK-Lightplanes FK12 Comet, is a single-engine, two-seat sports biplane designed in Germany. First flown in 1999, it was available as a kit or complete and ready-to-fly.

A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While a biplane wing structure has a structural advantage over a monoplane, it produces more drag than a monoplane wing. Improved structural techniques, better materials and higher speeds made the biplane configuration obsolete for most purposes by the late 1930s.