Etrian Odyssey Untold: The Millennium Girl from Atlus Games for the Nintendo 3DS is an RPG game in two parts.

The first part is a story-driven first person adventure into the world of Etria. Appropriate for players new to the series and veterans alike, the Story mode gives players five pre-made characters, each with their own personalities and dialogue to explore a side of Etria not seen in the first game. Adventurers must brave new dungeon layouts, floors, and enemies to find out the truth of the Yggdrasil Tree and the mysterious girl, Frederica.

For series veterans, Classic mode offers the traditional Etrian Odyssey gameplay, updated to the latest conveniences found in Etrian Odyssey IV, including full 3-D graphics. The game also includes animated opening and story cutscenes by MADHOUSE Inc. and voiceovers for the story and battle scenes, plus the option for orchestrated background music.