What is the name of the heavenly spear used to create the first island?

The heavenly spear used to create the first island is called Ame no Nuhoko, also written Ame-no-Nuboko.

In the Kojiki, the creator deities Izanagi and Izanami receive the jewel-adorned spear from older heavenly gods. Standing on the floating bridge between heaven and earth, they stir the primeval sea with it.

When Izanagi withdraws the spear, drops of briny water fall from its tip and coagulate into Onogoro Island, the first island in the creation story. The couple then descends to the island and begins the work of generating the Japanese archipelago and its kami.

English spellings vary because the name is transliterated from Japanese. Ame-no-Nuboko is a common scholarly form, while Ame no Nuhoko appears in other English references. It should not be confused with Ame-no-Sakahoko, a different legendary spear associated with later traditions involving Ninigi.