Abstract: An integrated ignition-transformer assembly for the cylinder of a heat engine having controlled ignition, the assembly being of the type comprising a tubular body (11) delimiting: an internal shoulder (12), mounting means (13) on one side of said shoulder for mounting on the stem of a spark plug (15), and a housing (14) on the other side of said shoulder containing an axially fixed transformer coil (24) which is encapsulated in a dielectric coating (25) and which includes a terminal (30) for making contact with the spark plug; said mounting means (13) being constituted by disconnectably fixing means for co-operating with a complementary thread provided on the base (17) of an adopted spark plug; and said terminal (30) being in contact with the terminal pin (35) of a spark plug and being surrounded by an internal sleeve (32) of dielectric material which extends said transformer coil (24) to said shoulder (12), and which is intended to receive, in sealed manner, the stem (16) of the spark plug on which the assem