The 66th Honinbo began league play on 7 October 2010 and completed on July 21, 2011. Title holder Yamashita Keigo retained his title over challenger Hane Naoki by a score of 4-3. Yamashita Keigo won the first three games, Hane Naoki the next three, and Yamashita Keigo the final game.
Preliminary tournament
The preliminary tournament started on 8 April 2010. Hane Naoki, Iyama Yuta, Takao Shinji, and Cho U retained their place in the Honinbo league from the 65th Honinbo. These players were joined by the winners of the preliminary tournament: Cho Sonjin, Seto Taiki, O Rissei, and Kobayashi Satoru.
League play
League play commenced on 7 October after the preliminaries, which finished on 2 September. Hane Naoki, who lost the Honinbo title to Yamashita Keigo the year prior, won the right to challenge Keigo for the title.