is a 2017 Japanese animated fantasy adventure film. It was produced by Signal.MD, written and directed by Kenji Kamiyama, and stars Mitsuki Takahata. It was released in Japan by Warner Bros. Pictures on March 18, 2017. An English dubbed version was released in the United Kingdom on August 16, 2017, and in the United States a month later. The theme song for the film is a cover of The Monkees' "Daydream Believer" performed by lead actress Mitsuki Takahata.

Plot

Napping Princess takes place in two concurrent settings: a near-future Japan, and Heartland, a fantastical realm. The main character, Kokone Morikawa, has strange dreams of Heartland while taking naps. In these dreams, Heartland is a society entirely revolving around cars; the King's castle is a car factory, and his subjects all come to it to make a constant stream of new cars. His daughter, Ancien (who appears as a younger Kokone), has a "magic tablet" computer she uses to give life to various machines: notably, a blue toy dog named Joy, and a motorcycle named Heart. The king disapproves of Ancien bringing Heart to life, however, and confiscates her tablet and Heart and orders Ancien to be confined to her tower. Additionally, the society of Heartland is under threat from a gigantic monster of molten metal called the Colossus. The king builds giant robots to face the Colossus. Ancien, spying a motorcycle-driving subject of the king's named Peach, decides to ally with him and seek to defeat the Colossus together with him, while the king's chief adviser Bewan plots against the king and Ancien alike.