was a Japanese samurai general in the Takeda army under Takeda Shingen, and later under Takeda Katsuyori.[1] He was known as one of the "Twenty-Four Generals of Takeda Shingen".
He was also lord of Iwadono Castle, and fought under the Takeda at the battles of Kawanakajima, Mikatagahara,[2] Nagashino and Tenmokuzan.
Oyamada betrayed Takeda Katsuyori in 1582, after Katsuyori's defeat at the Battle of Tenmokuzan;[3] however, when he went to the Oda clan camp, he was executed by Oda Nobunaga's officer Horio Yoshiharu.