A universal spark gap electrode with inner conductor formed as an elongate rod, an insulative sheath fit over the inner conductor, and an inner electrode tip soldered or brazed into the inner conductor. The inner conductor passes through an adapter and into an annular base with a spark gap cage and second electrode tip mounted thereon. The adapter is equipped with a molded annular jacket-type adapter mounted exteriorly thereon for engagement with the connecting receptacle of a lithotripsy machine. The annular base has a double-threaded collar that couples over the insulative sheath, and the adapter body screw-couples over the threaded collar of the annular base. This, the annular base, adapter body and insulative sheath are screw-coupled together in a coaxial configuration. Once the electrode is connected, the electrode tips generate a spark at the spark gap that vaporizes a small quantity of water, which creates an acoustic shock wave, which can be focused into the tissue of the patient and at a focal point corresponding to the position of a kidney stone or the like. A main advantage of the foregoing design is that the adapter can easily be substituted and replaced by an alternately-configured adapter to mate with other brands of lithotripters.