Yamanaka Sadayuki served as a bushō during the Sengoku period.  He was a retainer of the Amago clan.  He was the first individual to adopt the Yamanaka surname.  His first name was Muneyuki and then changed to Sadayuki.

In 1485, Sadayuki was born as the third son of Kuroda Harumune.

He headed to Izumo Province and served Amago Tsunehisa, a sengoku daimyō who wielded power in Izumo at this time.  Owing to his military achievements, Sadayuki became a general in the Amago army.  Thereafter, he became the lord of Shiraga Castle with a fief of 4,000 kan.  Later, he adopted the name of Yamanaka Ōkura-Tayū Sadayuki.  Known as a courageous warrior, he died at the age of seventy-six but, other than his service to Tsunehisa and being the first to adopt the Yamanaka surname, the details of his life are uncertain.