Lifespan: Ōnin 2 (1468) to 3/10 of Tenbun 7 (1538)
Lord: Amago Tsunehisa
Father: Yamanaka Yukimitsu
Mother: Daughter of Kawazoe Mitsuuji
Siblings: Katsushige, Mitsushige, sister (wife of Koshi Hōgan Mitsumasa)
Children: Mitsuyuki (?), Nobunao (?)
Yamanaka Katsushige served as a bushō during the late Muromachi and Sengoku periods. He was a retainer of the Amago clan and the grandfather of Yamanaka Yukimori, the head of the Ten Warriors of the Amago who led a campaign to revive the Amago clan. His real name was Mitsumori.
The Yamanaka clan were an illegitimate branch of the Amago clan founded by Yamanaka Yukihisa, the second son of Amago Kiyosada (the deputy military governor of Izumo during the mid to late Muromachi period). In 1468, Katsushige was born as the son of Yamanaka Yukimitsu.
In 1484, his lord, Amago Tsunehisa, was ousted by Kyōgoku Masatsune, the military governor of Izumo. Katsushige then became a rōnin, or wandering samurai, but, in 1485, Katsushige participated in a plan by Tsunehisa to recover his base at Gassantoda Castle. In 1486, Tsunehisa succeeded in recovering the castle. At this time, owing to his contributions on the battlefield, Katsushige became an elder of the Amago clan.
In 1488, Tsunehisa ordered Katsushige to serve as an official for Misawa Tameyuki, the head of the Misawa clan having influence in the Unnan area of Izumo. After serving loyally for two years, Katsushige then deceived Tameyuki by declaring his intent to eliminate Tsunehisa and leading an elite force of 500 soldiers from the Misawa army toward Gassantoda Castle. Upon arriving at the castle, only Katsushige entered. Unaware of the situation, the members of the Misawa army were then killed by the Amago army led by Tsunehisa. As a result, the Misawa and other kokujin, or provincial landowners, in Izumo came under the command of the Amago clan.
On 3/10 of Tenbun 7 (1538), he died at the age of seventy-one.
There are many mysteries with respect to Katsushige. Details after subduing the Misawa are uncertain. At the time when Katsushige was a rōnin and Tsunehisa visited him to share his intent to recapture Gassantoda Castle, Katsushige was said to have tearfully nodded in agreement. This demonstrated his deep loyalty toward his ousted lord. However, there is a lack of information in contemporaneous accounts regarding the recovery by Tsunehisa of Gassantoda, so there are questions regarding the details of these events.