Thráin II is the father of Thorin Oakenshield in J.R.R. Tolkien’s Middle-earth.
Thráin II was a dwarf of Durin’s Folk and became King of the Longbeards after the death of his father, Thrór. He is an important figure in the history leading to The Hobbit because the loss of the Lonely Mountain shaped the lives of his son Thorin and their people.
After Smaug drove the dwarves from Erebor, Thráin wandered in search of the lost kingdom. He was captured by the Necromancer at Dol Guldur and imprisoned there. Gandalf later found Thráin, but Thráin had lost the map and key intended for Thorin before dying.
The character can be confused with other dwarf kings named Thorin or with Dáin Ironfoot, who later became King under the Mountain. Thráin II is specifically Thorin Oakenshield’s father.