A gas burner with at least two flame rings, consisting of: - an injector holder provided with a single vertical injector positioned centrally on the base of said injector holder, - a flame divider with an outer chamber of overall annular development, and an inner chamber of overall circular development, between which an annular cavity is interposed, - a cover, and in said gas burner: - said flame divider comprises on its lower part resting means (30, 23) of said flame divider on said injector holder (6, 12), and its connection thereto, - the inner circular chamber of said flame divider comprises a single substantially vertical channel facing said single vertical injector of said injector holder, said substantially vertical conduit opening into a radial chamber of venturi effect defined in said inner chamber of the flame divider and upperly bounded by the central discoidal portion of said cover, - said flame divider comprises at least one substantially radial channel for fluidic connection between said inner circular chamber and said outer annular chamber, said radial channel being closed upperly by a corresponding radial part of said cover, - said at least two flame rings comprising a first ring of flames, generated at ports (42, 43) provided in the outer wall of said outer annular chamber of the flame divider, and at least one second ring of flames which can be generated at ports (42, 43) provided in the inner wall of said outer annular chamber of the flame divider, or at ports (42, 43) provided in the lateral wall of said inner chamber of the flame divider or at ports (42, 43) provided in both the inner wall of said outer annular chamber and said lateral wall of said inner circular chamber, - said cover is made in one piece and comprises a central discoidal portion, which upperly closes said inner circular chamber, and an annular portion which upperly closes said outer annular chamber, - said substantially vertical channel facing said single vertical injector is defined within a tubular conduit which extends downwards from the inner chamber of the flame divider, and characterized in that: - said injector holder (6, 12) is of dish shape and is provided with apertures for the intake of primary air from below a cooking hob in which said burner is to be installed, and in that said resting means (30, 23) comprise said tubular conduit, which is sealedly inserted into said dish shaped injector holder (6, 12). - an injector holder provided with a single vertical injector positioned centrally on the base of said injector holder, - a flame divider with an outer chamber of overall annular development, and an inner chamber of overall circular development, between which an annular cavity is interposed, - a cover, - said flame divider comprises on its lower part resting means (30, 23) of said flame divider on said injector holder (6, 12), and its connection thereto, - the inner circular chamber of said flame divider comprises a single substantially vertical channel facing said single vertical injector of said injector holder, said substantially vertical conduit opening into a radial chamber of venturi effect defined in said inner chamber of the flame divider and upperly bounded by the central discoidal portion of said cover, - said flame divider comprises at least one substantially radial channel for fluidic connection between said inner circular chamber and said outer annular chamber, said radial channel being closed upperly by a corresponding radial part of said cover, - said at least two flame rings comprising a first ring of flames, generated at ports (42, 43) provided in the outer wall of said outer annular chamber of the flame divider, and at least one second ring of flames which can be generated at ports (42, 43) provided in the inner wall of said outer annular chamber of the flame divider, or at ports (42, 43) provided in the lateral wall of said inner chamber of the flame divider or at ports (42, 43) provided in both the inner wall of said outer annular chamber and said lateral wall of said inner circular chamber, - said cover is made in one piece and comprises a central discoidal portion, which upperly closes said inner circular chamber, and an annular portion which upperly closes said outer annular chamber, - said substantially vertical channel facing said single vertical injector is defined within a tubular conduit which extends downwards from the inner chamber of the flame divider, - said injector holder (6, 12) is of dish shape and is provided with apertures for the intake of primary air from below a cooking hob in which said burner is to be installed, and in that said resting means (30, 23) comprise said tubular conduit, which is sealedly inserted into said dish shaped injector holder (6, 12).