See Also: World Oza
Oza (王座 Ōza), which literally means "throne", is the sixth of the seven big titles in Japanese professional Go. The winner's prize is ¥13,500,000 currently, sponsored by the Nihon Keizai Shinbun. All professional players of the Nihon Ki-in and Kansai Ki-in can participate.
The Oza shares most of its structure with the other big titles in Japan - the winner of a preliminary tournament (in this case a single knockout tournament) plays a best of five match against the previous year's title holder. This has been the case since the 16th Oza in 1968. Prior to that it was a best of three match between the final two players from the knockout tournament, making it much more difficult to be a repeat title holder (as only Hashimoto Utaro and Sakata Eio were able to achieve).
Due to the importance of the Oza 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.
 Prior to the 16th Oza in 1968, the title holder was required to play in the preliminary matches under the same conditions as all other participants. Therefore, repeating as Oza was significantly more difficult before the 16th Oza.