66th Honinbo
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.| Player | H.N. | I.Y. | T.S. | C.U. | O.R. | K.S. | C.S. | S.T. | Record | Notes |
| Hane Naoki | – | B+R | W+R | X | W+0.5 | B+R | W+R | B+R | 6–1 | Challenger |
| Iyama Yuta | X | – | B+R | X | X | W+R | B+R | W+R | 4–3 | |
| Takao Shinji | X | X | – | B+1.5 | X | X | W+R | X | 2–5 | Eliminated |
| Cho U | W+R | B+0.5 | X | – | B+3.5 | X | B+R | X | 4–3 | |
| O Rissei | X | W+R | B+R | X | – | X | X | B+R | 3–4 | Eliminated |
| Kobayashi Satoru | X | X | W+2.5 | B+4.5 | W+R | – | X | X | 3–4 | Eliminated |
| Cho Sonjin | X | X | X | X | B+R | W+11.5 | – | X | 2–5 | Eliminated |
| Seto Taiki | X | X | W+R | B+R | X | B+3.5 | W+R | – | 4–3 |