A daimyo of the Sengoku period, head of the Mōri clan based at Yoshida-Kōriyama Castle in Aki Province (present-day Akitakata City, Hiroshima). He lost his father Hiromoto in childhood and inherited the clan after the death of his elder brother Okimoto. Through stratagem, diplomacy, and strategy, he expanded his power; in 1540, at the Battle of Kōriyama, he drove off Amago Haruhisa of Izumo with aid from Ōuchi Yoshitaka. At the Battle of Itsukushima in 1555, he annihilated the vast army of Sue Harukata—who had seized power within the Ōuchi clan—by exploiting terrain and tidal flows, establishing his reputation as one of the greatest commanders of the Sengoku age. He then absorbed the former Ōuchi territories and subjugated nearly the entire Chūgoku region. His deathbed admonition to his three sons—the "lesson of the three arrows" (a single arrow breaks easily, but three bound together cannot)—is widely known as a symbol of Mōri family unity. He died at 75.

A coldly calculating strategist who nonetheless harbored deep love for his family. Dubbed a "master of intrigue" for his skillful manipulation of allies and enemies alike, his letters and precepts to his sons nonetheless reveal a warmly human side. He remained active throughout a long life.

The transformative founder who made the Mōri clan into a major Sengoku domain. The Battle of Itsukushima continues to be celebrated as a masterpiece of stratagem. The lesson of the three arrows is still cited today as a teaching on unity and cooperation, and he is one of Hiroshima Prefecture's iconic historical figures.