Through nonequilibrium low-temperature molecular beam epitaxy, we have grown GaN1−xBix alloys on sapphire substrates with x up to 0.11. The GaN1−xBix alloys are found to be amorphous with GaN crystals distributed throughout the film. A dramatic reduction in the optical band gap from 3.4 eV in GaN to as low as 1.2 eV for x ∼ 0.11 was qualitatively explained by formation of a narrow band originating from anticrossing interaction between Bi localized states and the extended states of the GaN matrix.