An object of the present invention is to provide an ignition coil which has a structure to make it possible to connect the ignition coil to a spark plug directly and in which an installation space need not be changed largely when the ignition coil is mounted in a cylinder head, and an internal combustion engine ignition system having the ignition coil.
In the present invention, a protection metal pipe (31) of an ignition coil (9) is formed so that a rear end side portion of a spark plug (11) in the rear of a rear end surface (23b) of a collar portion (23) in a metal shell (19) can be received in the inside of the protection metal pipe (31) from a front end (31b). The ignition coil (9) has a structure in which the ignition coil (9) is directly connected to the spark plug (11). The protection metal pipe (31) of the ignition coil (9) is formed to serve also as a plughole pipe, so that the outer diameter of the protection metal pipe (31) can be enlarged up to the outer diameter of a conventional plughole pipe. As a result, a space for installing a coil body portion (37) can be secured largely in the inside of the protection metal pipe (31), so that the installation space need not be changed largely when the ignition coil is mounted in a cylinder head.