The present invention provides a gas burner (10) including: a distributor means (50) having at least one distribution chamber to distribute an air gas mixture around said distributor (50), said burner (10) including a plurality of flame ports (70) through which said gas mixture can pass and be ignited; at least one injector (39) associated with said distributor (50), said at least one injector (39) being positioned to inject gas into said at least distribution chamber via a venture formed of a vertically directed passage and transition port (64) and at least one venturi extension extending away from said transition port (64). The present invention also provides manifold for a gas burner (10), said manifold having an upper wall (12) and a lower wall (16) held in spaced apart relationship by a peripheral wall to define a cavity there between, said manifold including means (38) to mount at least one injector (39) so as to deliver an air gas supply to a distribution means (50) and an inlet port (18) to allow connection to a supply of gas, which can pressurize said cavity, said upper (12) and said lower (16) wall being formed from relatively thin sections.