The Z Sword was the legendary sword that was on the Kaiohshin World.
In a meeting with the Kaiohshin and Gods of Destruction, the Gods of Destruction Beerus sealed Roh-Kaiohshin in the Z Sword over a trifling situation, as destroying the Kaiohshin would have been improper. The sword has since then been kept on the Kaiohshin World inside a rock. Son Gohan was the first to retrieve the legendary blade from the rock and trained with the sword. When the East Kaiohshin, Shin, suggested testing the sword's sharpness by cutting Katchin Steel, the sword broke when Gohan attempted to cut the hardest metal in the universe. After the sword broke, Roh-Kaiohshin was released from the sword.
In Trunks's future, Trunks was invited to the Kaiohshin World by Shin and allowed him to train with the Z Sword because of Babidi attempting to revive Majin-Boo. In the battle with Babidi and Darbura, the sword was wielded by Trunks but was turned into stone and immediately burned.