Japan's first empress regnant (r. 593–628), born as a princess of Emperor Kinmei. After serving as consort of Emperor Bidatsu, she ascended the throne following the assassination of Emperor Sushun. She appointed her nephew Prince Shōtoku as regent and, together with Soga no Umako, the three collaborated to establish a centralized state. She oversaw the creation of the Twelve-Level Cap and Rank System (603) and the Seventeen-Article Constitution (604)—Japan's earliest written governance norms—and actively promoted Buddhism as a state religion. In 607, she dispatched Ono no Imoko to Sui China on a diplomatic mission asserting equal standing ("from the Son of Heaven of the land where the sun rises…"). Her reign of 35 years guided the golden age of Asuka culture. She died in 628 at the age of 75.

A ruler of strong will and flexible insight. She reigned with authority in a male-dominated court, skillfully mediating between Prince Shōtoku and Soga no Umako while driving sweeping reform. She was also known for her deep personal devotion to Buddhism.

As Japan's first empress regnant, she set a precedent for future female rulers. The cap-rank system, the constitution, and the Sui missions laid the groundwork for the later ritsuryō state, while official recognition of Buddhism underpinned the flourishing of Asuka culture.