Abstract: Disclosed is a spark plug for an internal combustion engine including an annular end portion with a central electrode having an end within the annular end portion. A ground electrode extends from the annular end portion and has a portion extending over and spaced a predetermined distance above the end of the central electrode. The improvement comprises the end of the central electrode having cross-grooves therein defining four end faces and the ground electrode having diverging prongs at its end over the central electrode, a portion of each prong being over two adjacent end faces of the central electrode. Improved ignition is provided without critical manufacturing problems of prior art spark plugs.