Age of Empires II: The Forgotten is the second official expansion pack for Age of Empires II. It features five new civilizations, (the Incas, Indians, Italians, Magyars and Slavs), new units and technologies, new maps, enhanced AI, a higher population limit, greater on-screen rendering, bug fixes and several tweaks to old units, technologies, and bonuses for improved gameplay balance.

Originating as a fan-made modification (before they became Forgotten Empires Studios) entitled Age of Empires II: The Forgotten Empires, the expansion was developed with SkyBox Labs and released in 2013 exclusively on Steam. It requires the Age of Empires II HD Edition for installation.