A fictional triple-decker bus, the Knight Bus, is part of the story created by J. K. Rowling in her book Harry Potter and the Prisoner of Azkaban.

This AEC Regent III RT bus with decks, featured in the 2004 film of the same name, provided transportation for stranded members of the Wizard fraternity. All the wizard had to do was stick their wand hand in the air and the driver, Ernie Prang, would stop. Inside the bus was conductor Stan Shunpike, who would help passengers with their bags.

This bus had seats during the day but in the night had candles burning in brackets beside the window curtains. This bus could travel at breakneck speed and squeeze through any gap and brake in an instant, enabling it to reach any destination (except those underwater).

This bus came to Harry Potter's rescue before he began his third year at Hogwarts.