Age of Empires II (abbreviated as AoE2, or AoK in the old days, because of the subtitle "The Age of Kings") is a real-time strategy game developed by Ensemble Studios and published by Microsoft. It was released in 1999 for Microsoft Windows and it is a sequel of Age of Empires, the first one of the series.

AoE2 is set in the Middle Ages and was released with thirteen playable civilizations and focuses on building towns, gathering resources, and creating armies to defeat opponents. Players conquer rival towns and empires as they advance one of civilizations through "Ages": the Dark Age, the Feudal Age, the Castle Age, and the Imperial Age. Advancing to a new Age unlocks new units, structures, and technologies.

The expansion pack "The Conquerors" (AoC), developed by Ensemble Studios and published by Microsoft too, was released in 2000 and featured five new civilizations, new campaigns, new units, new technologies, new gameplay modes, new maps and different minor tweaks to the gameplay.

On April 9, 2013, Age of Empires II: HD Edition (AoE2HD) was released. The game, a HD remaster of the original game, was developed by Hidden Path Entertainment and published by Microsoft Studios, and came with improved graphics, widescreen support as well as new multiplayer options through Steam.

The following years, the HD Edition received three expansions: The Forgotten, The African Kindgoms, and Rise of The Rajas. The first one was based on the fan-made expansion, The Forgotten Empires. All expansions introuced new civilizations, maps, campagings, units, game mode and numerous balance and gameplay adjustments.

To celebrate the 20th anniversary of the original game, Age of Empires II: Definitive Edition (AoE2DE) was released on November 15, 2019. The game was developed by Forgotten Empires, Tantalus Media and Wicked Witch and published by Xbox Game Studios. It features significantly improved visuals, supports 4K resolution, a new single player campaign and four new civilisations. It also includes all previous expansions from the original and HD edition.

The competitive scene of the game has existed since its early years, with the support of large companies and organizations, and with the important participation of its community, and continues to the present day.

In the past, Microsoft has promoted its own championships, just as World Cyber Games has included the game in some of its editions, but people around the world on their own have organized major tournaments to foster the competitive scene and reward the best players and teams.