Mori Motomura served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a retainer of the Miyoshi family and served as the lord of Tosadomari Castle. His common names were Shima-no-kami and Chikugo-no-kami.
Motomura was born as the son of Sada Kurōzaemon. Initially, Motomura resided in the village of Kuroda in the Myōdō District of Awa but, later, moved to Tosadomari in the Itano District. During the Tenbun era (1532 to 1555), he built Tosadomari Castle. The castle was strategically located at the entrance to the Kii Channel and Seto Inland Sea.
In 1539, when Hosokawa Harumoto engaged in battle against the Kōno clan, Motomura participated by leading naval forces.
In 1582, after an invasion by Chōsokabe Motochika, the sengoku daimyō of Tosa Province, almost all of the castles in Awa and Sanuki provinces fell to the Chōsokabe, except Motomura was able to withstand the assault from Tosadomari Castle.
In 1585, following the Conquest of Shikoku by Toyotomi Hideyoshi, Hachisuka Iemasa, a daimyō and retainer of Hideyoshi came to Shikoku whereupon Motomura received recognition of the rights to landholdings of 3,026 koku. In 1586, he moved to Tsubakidomari.
Motomura died of illness in 1594. His eldest son, Mori Muraharu, preceded him in death in battle in the Bunroku Campaign on the Korean Peninsula.