Blue Hole (Japanese: ブルーホール, Hepburn: Burū Hōru) is a Japanese manga series written and illustrated by Yukinobu Hoshino. It was serialized in Kodansha's seinen manga magazine Mr. Magazine from 1991 to 1992, with its chapters collected in two tankōbon volumes. A sequel, titled Blue World, was serialized in Monthly Afternoon from 1995 to 1997, with its chapters collected in four volumes. The story is about the discovery of a gateway in time and space deep underwater which allows for travel between the present day and the age of the dinosaurs.