Emperor Saga (嵯峨天皇) (786-842) was the 52nd imperial ruler of Japan. He was the second son of Kammu, and younger brother of Heizei, his predecessor. He ruled from 809 to 823.

Saga was a scholar of the Chinese classics and, according to legend, the first Japanese emperor to drink tea. He was renowned as a skillful calligrapher. Saga succeeded to the throne after the retirement of Heizei due to illness, and soon after his enthronement was himself ill. This gave Heizei an opportunity to forment a rebellion, which Saga put down in a bloody civil war.

Saga was a supporter of the Buddhist monk Kukai and helped him to establish the Shingon School of Buddhism by granting him the Toji temple in the capital Heian (present day Kyoto).