Hon'inbō Dōsaku (1645–1702) was a professional Go player. Dōsaku was one of the greatest Go players in history. He was born in the Iwami Province of Japan and studied Go in the Hon'inbō school, becoming Meijin at a very young age.

Dōsaku was the fourth Hon'inbō by the time he was 32, and the fourth Meijin by the time he was 33. He started to learn Go at 7. Dōsaku was so strong by the time he was in his early 20s that even if someone played the first move, he would always win. Rumors were that he was two stones stronger than any other Go player. This was due to his deep thinking and next-level tactics. He laid the foundation for opening strategy in the Golden Period.