What giant spider attacks Frodo in Shelob's Lair?

The giant spider that attacks Frodo in Shelob’s Lair is Shelob. She lives in Torech Ungol, a vast lair beneath Cirith Ungol on the border of Mordor. Gollum deliberately guides Frodo and Sam toward her tunnels, hoping Shelob will kill them so he can reclaim the One Ring.

Tolkien describes Shelob as an ancient and immensely powerful spider, the last child of Ungoliant to trouble the world. She is independent of Sauron, serving no master, although Sauron tolerates her presence because she helps guard the pass into Mordor. The Orcs call her “Shelob the Great” and treat her as a terrifying local power.

Shelob paralyzes Frodo with her venom, but Sam fights back using the Phial of Galadriel and Frodo’s sword, Sting. The light drives her away, while Sting wounds her when she attacks Sam. “Attercop” is a general old term for spider in Tolkien’s works, and Mirkwood contains other giant spiders, but neither is the specific creature in Frodo’s lair. In the film trilogy, Shelob appears in The Return of the King.