Gas burner provided with a plurality of concentric flame crowns, and comprising a first central burner to supply a peripheral flame ring, a second annular burner surrounding the central burner at a defined distance and able of supplying at least a respective peripheral ring, a burner body apt to be mounted on the surface of a cooking hob, a first gas inlet in communication with the body, a first vertical gas injector, the central burner being provided with a first chamber for the diffusion of the air/gas mixture, a second gas inlet in communication with the body, wherein the second annular burner is provided with two separate chambers for the diffusion of the mixture, wherein the second gas inlet is in communication with the two separate chambers through suitable injection and conveying means, which comprise two distinct injectors in communication with the second gas inlet, and two respective horizontal Venturi pipes each of which being able of supplying with the air/gas mixture a respective of the two diffusion chambers; these are physically separate and not in communication to each other. The two horizontal and separate injectors are placed on the same end position of the second gas inlet.