The Valley of the Lost is the seventh book in the Deltora Quest novel series written by Emily Rodda.

After having reached the Maze of the Beast and finding the amethyst, they continue their journey off to the Valley of the Lost to retrieve the seventh and final gem, the diamond.

Realizing that it was the ship that a boy named Dain was captured aboard upon, they steal a rowboat in an attempt to rescue him.

The diamond curses those who gain the gem by theft, and Neridah dies by tripping on a rock and drowning in a stream.

Knowing that they have all seven gems, the three travel with Dain back to Del to find the king who will put on the Belt to banish the Shadow Lord from Deltora.