Yasunaga Hajime (安永 一, 1901-February 2, 1994) was the strongest and most famous amateur Go player of the 20th century in Japan.

In the early 1930s he co-wrote Shin Fuseki Ho, a seminal work on go opening theory, in cooperation with the young professionals Kitani Minoru and Go Seigen.

The book created a sensation, and helped win amateur players over to the revolutionary ideas of shin fuseki ("new opening") theory.

He also taught a number of professionals, including Komatsu Hideki and Kageyama Toshiro and Yokoyama Koichi.

It has been said that at his peak, Yasunaga was sometimes able to defeat inexperienced young professional players while giving them two-stone handicaps.