The Desert River of Oblivion was a river of sand situated in Sagittarius Zero Star, which had the power to make people forget everything. The river was guarded by Sailor Lethe.
When Sailor Moon, Sailor Chibi Chibi Moon, the Starlights, and Princess Kakyuu arrived at Sagittarius Zero Star, they encountered Sailor Lethe in disguise, who lured them out onto the river in a boat. When the sand abruptly turned to water the boat sank, and Sailor Moon and her friends fell into the river, causing them to lose their memories.
The river was close to the Desert River of Memory guarded by Sailor Mnemosyne, which had the power to negate the effect of this river.
- The Desert River of Oblivion which was guarded by Sailor Lethe is a direct reference to the river Lethe in Greek mythology, from which the dead entering Hades drank in order to forget their past life.