Mariyatsu Zenhō was an individual who lived during the Sengoku period.  He was a member of the Mariyatsu-Takeda (Kazusa-Takeda clan).

Zenhō was born as the son of Mariyatsu Nobukatsu.  He was the younger brother of Mariyatsu Jokan (Nobukiyo).  After entering the priesthood, he adopted the names of Zenhō and Shinseisai.

His real name is unknown but is surmised to have been Nobuyasu.  Alternatively, he appears to have also used the name of Nobuaki.

In 1534, after the death of his older brother, Jokan, a succession struggle erupted between Jokan’s eldest (illegitimate) son, Mariyatsu Nobutaka, and Jokan’s younger lineal heir, Mariyatsu Nobumasa.  Zenhō actively supported Nobumasa and, in 1537, Nobumasa eventually prevailed.  Through the mediation of Satomi Yoshitaka, Zenhō settled with Hōjō Ujitsuna who was allied with Nobutaka whereupon Nobutaka’s base at Minegami Castle was turned over to Zenhō.  Thereafter, Zenhō served as Nobumasa’s deputy in negotiations with the Oyumi kubō.  His movements from 1542 onward cannot be confirmed from authenticated sources.  His son, Mariyatsu Yoshinobu, became the lord of Sanuki Castle.