What is the name of the giant spider Bilbo fights in Mirkwood in J.R.R. Tolkien’s The Hobbit?

The giant spider Bilbo fights in Mirkwood in J.R.R. Tolkien’s The Hobbit has no individual name in the text.

Bilbo encounters the spiders after the company of Dwarves becomes trapped in the dark forest. The spiders bind the Dwarves in webs and carry them toward their lair. Bilbo, wearing the One Ring, moves unseen and attacks them with his sword. He names that sword Sting after killing one of the spiders, then uses stones and quick movement to drive the others away and rescue the prisoners.

Tolkien describes these creatures collectively as giant spiders rather than identifying one with a personal name. This is different from Shelob, the enormous spider encountered by Frodo and Sam in Cirith Ungol in The Lord of the Rings. Shelob is an individual and is connected in the text to the older spider-being Ungoliant, but she is not the named spider from Bilbo’s Mirkwood battle.

Later adaptations and fan discussions sometimes supply labels or treat one spider as a distinct character. Tolkien’s published narrative does not do so. The precise answer is therefore that Bilbo’s Mirkwood opponent is unnamed.