Provided is a gas burner (100, 200, 300), preferably for domestic use, of the type comprising at least one fuel gas injector (9, 209, 309) and at least one corresponding Venturi effect mixer (10, 210, 310a, 310b), wherein the above-mentioned injector (9, 209, 309) faces the intake section of said Venturi effect mixer (10, 210, 310), and one or more passages (8, 208, 308) for the transit of primary air from above the supporting surface (7, 307), to which the burner (100, 200, 300) is fixed, to the intake section of the Venturi effect mixer (10, 210, 310a, 310b). The burner (100, 200, 300) is also provided with means for preventing flame propagation, of the fluid flow splitting type, which comprise at least one substantially tubular body (11, 211, 214, 311 ), with relative lateral walls extending at least between the injector (9, 209, 309) and the intake section of the Venturi effect mixer (10, 110, 110a, 110b), advantageously consisting of at least one helically wound filiform element.