Shelob is the giant spider defeated by Sam in J.R.R. Tolkien’s The Two Towers.
Shelob attacks Frodo and Sam in the pass of Cirith Ungol while they are traveling toward Mordor. She poisons Frodo, but Sam uses the sword Sting and the Phial of Galadriel to drive her away. Believing Frodo dead, Sam briefly takes the One Ring before learning that Frodo is alive.
Shelob is not an ordinary giant spider. Tolkien describes her as a descendant of Ungoliant, an ancient and immensely powerful spider-like being from the mythology of the First Age. Shelob’s lair and the tower above the pass form one of the story’s most dangerous locations.
The encounter appears in The Two Towers, although the immediate consequences continue into The Return of the King. Shelob is therefore distinct from the spiders Bilbo encounters in Mirkwood in The Hobbit.