Which studio developed Star Wars Knights of the Old Republic II: The Sith Lords?

Star Wars Knights of the Old Republic II: The Sith Lords was developed by Obsidian Entertainment.

Obsidian made the sequel after BioWare, the developer of the original Knights of the Old Republic, suggested that the studio take over the project. LucasArts chose Obsidian partly because its team had experience with the technology and with large, story-driven role-playing games.

Development began in October 2003, and the game was released for Xbox on December 6, 2004, followed by the Windows version on February 8, 2005. LucasArts published the game, so publisher and developer are common sources of confusion in this question.

The Sith Lords uses the same Odyssey Engine as BioWare’s original game and continues the series roughly five years after its events. Obsidian’s writing, companion characters, and morally complicated story earned praise, although the rushed production also left visible bugs and cut content. BioWare therefore belongs among the answers only for the first game, not for the sequel.