Gram was forged by Volund; Sigmund received it in the hall of the Völsung after pulling it out of the tree Barnstokkr where Odin placed it. The sword was destroyed in battle when Sigmund struck the spear of an enemy dressed in a black hooded cloak. Before he died, Sigmund instructed his wife to keep the pieces so that it might be reforged for their unborn son (Sigurd). The sword was eventually reforged by Regin for Sigurd's use. After it was reforged, it could cleave an anvil in half.
In the Nibelungenlied (ca. 13th century), Siegfried says that the name of this sword is Balmung; in Richard Wagner'sRing Cycle (1848–1874), it is called Nothung. The name of the sword seemingly changes depending on the story that you consider.