Iwate Tsunayoshi served as a bushō during the Sengoku period.  He was a member of the Takeda clan and the granduncle of Takeda Harunobu (Shingen).  Tsunayoshi may also have been pronounced as Tsunamitsu based on the characters used in an authenticated letter from the Miura family.

Tsunayoshi was born as the fourth son of Takeda Nobumasa, a shugo daimyō and the thirteenth head of the Kai-Takeda clan.

Tsunayoshi’s landholdings were in the Iwate township of the Yamanashi District of Kai Province, so he adopted the surname of Iwate.  In 1505, his father, Nobumasa, and, in 1507, his eldest brother, Takeda Nobutsuna, died in succession.  After his nephew, Takeda Nobutora (the designated heir of Nobutsuna) became the next head of the Takeda family, Tsunayoshi joined with his second oldest brother, Aburakawa Nobuyoshi, to rebel against Nobutora.

On 10/4 of Eishō 5 (1508), Tsunayoshi suffered a major defeat to Nobutora at the Battle of Katsuyama where he was killed in action along with Nobuyoshi and family members.  This marked the end of the succession struggles that had persisted in the Takeda family from the era of Nobutsuna, firmly establishing Nobutora as the head of the clan.

The Iwate family was allowed to continue in existence and the headship of the clan was inherited by his orphan, Iwate Nobumori.