Gatlantis refers to an alien civilization that threatens Earth at the start of the twenty-third century. You may be looking for:
- Gatlantis (OS), a mobile space battle fortress and home of the White Comet Empire in Farewell to Space Battleship Yamato and Space Battleship Yamato 2
- The Gatlantis people and culture and/or the Gatlantis Empire in Space Battleship Yamato 2199 and its sequels
