Merkury Vagin (Russian: Меркурий Вагин) (died 1712) was a Russian Arctic explorer.
In 1712, together with Yakov Permyakov, Merkury Vagin explored the region of the eastern Laptev Sea coast. His exploration included Bolshoy Lyakhovsky Island, the southernmost of the New Siberian Archipelago. With a group of Cossacks they crossed the Yana Bay over the ice from the mouth of the Yana; after reaching Bolshoy Lyakhovsky, they explored the then unknown island that had been reported by Permyakov two years earlier.
Vagin and Permyakov were murdered on the way back from their exploration by mutineering expedition members. The cossacks took the dead bodies down to the ice and set them on fire. No one knows what the rebellious cossacks did with the ashes, but Merkury Vagin's remains were never found.
Merkuriya Island was named after this pioneering Russian explorer.