Judan (十段 Jūdan), which literally means "ten dan", is the fourth of the seven big titles in Japanese professional Go. The winner's prize is ¥14,500,000 currently, sponsored by the Sankei Shinbun newspaper. All professional players of the Nihon Ki-in and Kansai Ki-in can participate. The prize is 12 million yen, the sixth largest of the big titles.
Main article: Judan Preliminary Tournaments
The Judan shares most of its structure with the other big titles in Japan - the winner of a sixteen member preliminary tournament plays a best of five match against the previous year's title holder. The Judan is unique though in using a double knockout format to determine the challenger. Anyone who loses a game in the preliminary knockout tournament goes to a parallel tournament, the losers' section. At the end the winner of the loser's section plays the winner of the winner's section to decide who becomes the challenger. The original idea for this is attributed to Fujisawa Hosai.
The format changed in the 50th edition, by switching to an usual knockout tournament with 24 players.
Due to the importance of the Judan as one of the "big seven" titles in Japan, there are several paths of automatic rank advancement through it in the Nihon Ki-in new promotion system. Challenging for the title warrants a promotion to 7-dan, actually winning the title promotes to 8-dan, and finally winning the title twice gives an immediate 9-dan promotion.