Abstract: A prechamber spark plug for igniting a fuel-air mixture in an internal combustion engine, in particular a gas engine, having a spark plug body (1) comprising a prechamber housing (2) and a cap (4) that closes the prechamber (3) at least partially, a ground electrode (10) and a central electrode (7) isolated from the ground electrode and projecting into the prechamber, is designed and developed with simple structural means in order to obtain advantageous igniting properties, the ground electrode (10) being designed for that purpose essentially as a cylindrical pin (11) that can be welded in a passage (12), preferably a bore (12), in the spark plug body (1).