The Z sword is a legendary sword in that is located on the planet of the Kai wedged into a giant stone pillar, very similar to Excalibur. The legend of the sword is that whoever may withdraw it and master it will have the power to defeat any foe.

In the hope of defeating Majin Buu, Supreme Kai revives Son Gohan so that he may withdraw the sword and use it on Buu. Son Gohan, using his stregnth withdraws the sword and trains with it despite its extreme weight. During some training with his father Son Goku, the Z sword breaks and releases Old Kai.