Gas burner provided with a plurality of concentric and preferably circular flame crowns, and comprising: - a first central burner able of supplying a peripheral flame ring, - a second annular burner surrounding said central burner at a defined distance and able of supplying at least a respective peripheral flame ring (9, 10), - a burner body apt to be mounted on the surface of a cooking hob, and including: - a first gas inlet in communication with said body, - a first gas injector whose axis is vertically oriented, - said central burner being provided with a first chamber for the diffusion of the air/gas mixture, and with a plurality of ports to let said mixture out, placed on its upper edge and whose top is closed by a first cover, - a second gas inlet in communication with said body, wherein said second annular burner is provided with a plurality of ports (9, 10), to let said mixture out, placed on the relevant upper edge and whose top is closed by a second cover, characterized in that the second annular burner is provided with two separate chambers (21, 22) for the diffusion of said mixture, wherein said second gas inlet is in communication with said two separate chambers (21, 22) through suitable injection and conveying means, said injection and conveying means comprise: - two distinct injectors (15, 16) in communication with said second gas inlet, and - two respective Venturi pipes which are placed in horizontal (17, 18), each of which being able of supplying said air/gas mixture with a respective of said two diffusion chambers (21, 22), - and wherein said Venturi pipes (17, 18) are so sized and angulated to each other so that they enter not into the circumferential extreme side (21B, 22B) of said respective gas diffusion chambers (21, 22), but in respective zones (21A, 22A) which are far from said extreme sides (21B, 22B) by making said two Venturi pipes (17, 18) to diverge, - and wherein the the introduction of the Venturi pipes (17, 18) into said zones (21A, 22A) of the respective chambers splits the gas flow into two separate, and basically opposed at 180° flows, each of them going into a respective portion the gas diffusion chamber (21, 22). - a first central burner able of supplying a peripheral flame ring, - a second annular burner surrounding said central burner at a defined distance and able of supplying at least a respective peripheral flame ring (9, 10), - a burner body apt to be mounted on the surface of a cooking hob, and including: - a first gas inlet in communication with said body, - a first gas injector whose axis is vertically oriented, - said central burner being provided with a first chamber for the diffusion of the air/gas mixture, and with a plurality of ports to let said mixture out, placed on its upper edge and whose top is closed by a first cover, - a second gas inlet in communication with said body, - two distinct injectors (15, 16) in communication with said second gas inlet, and - two respective Venturi pipes which are placed in horizontal (17, 18), each of which being able of supplying said air/gas mixture with a respective of said two diffusion chambers (21, 22), - and wherein said Venturi pipes (17, 18) are so sized and angulated to each other so that they enter not into the circumferential extreme side (21B, 22B) of said respective gas diffusion chambers (21, 22), but in respective zones (21A, 22A) which are far from said extreme sides (21B, 22B) by making said two Venturi pipes (17, 18) to diverge, - and wherein the the introduction of the Venturi pipes (17, 18) into said zones (21A, 22A) of the respective chambers splits the gas flow into two separate, and basically opposed at 180° flows, each of them going into a respective portion the gas diffusion chamber (21, 22).