The Elder Scrolls IV: Knights of the Nine is an official expansion pack for the role-playing video game The Elder Scrolls IV: Oblivion. Announced on October 17, 2006 for release on November 21, 2006, the expansion was developed, published, and released in North America by Bethesda Softworks; in Europe, the game was co-published with Ubisoft. The Windows version is available either as a downloadable plug-in from the company website or as part of the retail-released Oblivion Downloadable Content Collection CD—a release that also includes all previously released official downloadable content available for Oblivion. The Xbox 360 version is available via Xbox Live Marketplace, and the PlayStation 3 version of Oblivion includes Knights of the Nine in its packaged release.