Yamamoto Yasutada served as a bushō during the Azuchi-Momoyama period.
Yasutada was the last head of the Kii-Yamamoto clan and the lord of Ryūshōzan Castle in Kii Province.
Around 1560, Yasutada was born as the son of Yamamoto Tadatomo. In 1566, following the death of his father, a succession struggle ensued against his uncle, Yamamoto Hiromoto. Hiromoto garnered support from neighboring clans, including the Oyama and Atagi clans (who were kokujin, or provincial landowners), but through the actions of a senior retainer named Tagami Tomoyasu (Ukyō-no-jō) and family members, Yasutada prevailed and inherited the headship of the clan.
From 1585, Yasutada was subject to the Conquest of Kishū by Toyotomi Hideyoshi, and held out at his base at Ryūshōzan Castle for three months, but, while attending a settlement negotiation the following year, he was slayed by Tōdō Takatora and the Yamamoto clan was extinguished.