Abstract: A spark plug is provided including a housing, a center electrode and an outer electrode. The center electrode has a firing tip extending out from the housing. The outer electrode has an annular surface surrounding the center electrode. The annular surface is formed with a toroid shape. The crest of the toroid shape is arranged to face towards the center electrode. The annular surface and the firing tip of the center electrode define a gap to convey a spark. The gap is defined at least in a plane substantially perpendicular to a center axis of the spark plug. In another embodiment of the invention, the outer electrode can include an end portion having a planar surface with a circular shape and an aperture defining an annular surface surrounding the center electrode.