Heizei was a Japanese emperor who reigned from 806 to 809 AD during the Heian period. His reign is noted for the promotion of Buddhism and the arts, as well as efforts to strengthen the central government. Heizei was the son of Emperor Kanmu and was known for his interest in religious matters. After his abdication, he became a monk and took the name Kōkō. His reign was relatively short, but it laid the groundwork for future developments in Japanese culture and governance.