The Nightmare King is the main antagonist of the 1989 animated Japanese-American adventure fantasy film, Little Nemo: Adventures in Slumberland. He is the ruler of the dreaded Nightmare Land. He was voiced by both two late actors: Tarō Ishida in the Japanese adaption and Bill Martin in the English adaption. Martin was also the voice of the Shredder in the original Teenage Mutant Ninja Turtles animated television series.