The dwarf who forged Stormbreaker is Eitri. In Avengers: Infinity War, Thor travels to Nidavellir with Rocket and Groot to ask Eitri to create a replacement weapon after Hela destroys Mjolnir.
Eitri is the king of Nidavellir’s dwarves and one of the Marvel universe’s greatest weaponsmiths. Thanos previously forced Eitri and the other dwarves to forge the Infinity Gauntlet. Afterward, Thanos massacred the dwarves and crippled Eitri’s hands so he could never forge another weapon.
Thor helps restart Nidavellir’s damaged star-forge, while Rocket identifies the weapon’s design and Groot provides the wooden handle. Eitri completes the Stormbreaker head, making him the principal smith even though Thor, Rocket, and Groot all contribute to its creation.
The name can be confusing because Eitri is also called Sindri in Norse mythology and some Marvel comic contexts. Brok and Sindri are associated with other legendary weaponsmithing stories, but in the MCU, Eitri is the named dwarf responsible for Stormbreaker.