Yokei (919 - April 5, 991) was a Buddhist monk of Tendai Sect in the mid-Heian period. His secular surname was Usa clan. Though he is believed to have hailed from Sawara County in Chikuzen Province, some say that he hailed from Hyuga Province. His posthumous title was Chiben. He was also called Kannonin Sojo.
He studied Tendai doctrine under Myosen, a monk of Mt. Hiei, and received kanjo (ceremony to be the successor) from Gyoyo. Although he was appointed to the chief priest of Onjo-ji Temple in 979 followed by the chief priest of Hossho-ji Temple in 981, he resigned from his post due to the objections of the Sanmon school, which was descended from Ennin. He was inaugurated as the chief priest of Enryaku-ji Temple in 989, but due to the objections of the Sanmon school, he again resigned three months after his inauguration. He, however, was conferred the title of Gon no Sojo (a title of high-ranking priest) in the same year. In Senmyo (written Imperial edict) issued at that time, believers of Sanmon school were likened to parasites in a lion. Although the Jimon school, which was descended from Enchin, increased its influence thanks to Yokei, this became the beginning of the subsequent severe confrontation between the Sanmon school and the Jimon school.