Digimon Masters, also known as Digimon Masters Online, is a free-to-play massively multiplayer online role-playing game (MMORPG) with microtransactions. The game is based on the Digimon media franchise, specifically the universe and characters of the fifth anime series, Digimon Data Squad (though many aspects of Digimon Adventure, Digimon Adventure 02, Digimon Tamers, Digimon Frontier, and Digimon Fusion are incorporated). The game was first released in South Korea on October 30, 2009. An English version was scheduled to be released in December 2010 by WeMade Entertainment (the company responsible for the English Version of Digimon Battle), but it was delayed to 2011. It was announced in July 2011 that Joymax, a subsidiary of WeMade Entertainment, would publish the English version of the game. On August 30, 2011, Joymax held a pre-CBT for players, which ended on September 6, 2011. After the conclusion of the pre-CBT, Joymax announced on September 22, 2011, that the OBT will be held on September 27. The OBT for Digimon Masters concluded on October 11, 2011, with the game going into commercial service globally on October 20, 2011, except for some countries, including Japan and Indonesia.

In June 2022, a remaster of the game was announced, with the game engine changing to Unity and a target release date of the second half of 2023.