Paper Mario: The Thousand-Year Door is the second installment in the Paper Mario series, with the first being Paper Mario. It was released for the Nintendo GameCube in 2004.

The plot of the game revolves around Mario, who embarks on a mission to collect the seven Crystal Stars in order to open the Thousand-Year Door. After learning that Princess Peach has been kidnapped, he also sets out on a mission to rescue her from the X-Nauts. The game has intermissions between each chapter, in which the player assumes the role of Bowser, as well as Peach, who have their own stories that complement the main plot.