Dungeon Fighter Online, known in South Korea as Dungeon & Fighter,[a] is a multiplayer beat 'em up action role-playing game, developed and published for personal computers by Neople, a South Korean subsidiary of Nexon, and originally published by Hangame in 2005.

The game was originally released in South Korea as Dungeon & Fighter, then in Japan as Arad Senki,[b] and then published in China by Tencent.

Dungeon Fighter Online is one of the most-played and highest-grossing video games of all time, with over 850 million players worldwide and over $22 billion in lifetime revenue as of June 2023.

[6] Dungeon Fighter Online is similar to 2D side-scrolling arcade hack and slash/beat 'em up games, such as Golden Axe or Double Dragon.

There are a number of social aspects to Dungeon Fighter Online, including Guilds, PvP Arenas, and Party Play.

With this in mind, Neople looked for similar but different genres and ended up using belt-scrolling games such as Dynasty Wars and Cadillacs and Dinosaurs as an inspiration for making Dungeon Fighter Online an RPG.

Hi-res is not a likely path the game will take because director Yun Jong Kim's main focus is "efficiency".

[8][14] Five years after the original release in Korea, Nexon America developed plans for an English version of Dungeon Fighter Online.

[37] By March 2018, Dungeon Fighter Online was the highest-grossing PC game of the month, above League of Legends.

[35][36][40][41] As of May 2020, Dungeon Fighter Online has exceeded $15 billion in lifetime gross revenue, making it one of the highest-grossing entertainment media IPs, with its lifetime revenue larger than the box office gross of the Star Wars, Harry Potter and Avengers film series.