Dungeon Fighter Online is a free-to-play multiplayer hack-and-slash RPG with a side-scrolling arcade style. There are currently 11 unique character classes. 3 classes have a mirrored class of the opposite gender with a 4th being added soon. Classes have Sub-classes to choose from and later has advancements of those classes to unlock upgraded skills. Of the 11 unique classes, 6 have 4 sub-classes, 3 have 2 sub-classes, and 2 have no sub-classes but still has advancements for new skills.

Developed by the Korean company Neople in 2005 the game was released in Japan in 2006, China in 2007, Taiwan in 2009, and North America in 2010. The publisher Nexon shut the North American version down in 2013. Neople relaunched the game globally in 2016, with Season 2, adding new content and characters to the game.

The game was released on the Xbox 360 Arcade under the title "Dungeon Fighter Live".