An eighth-generation grandson of Shinran (1173–1262), the founder of the Japanese Pure Land school of Jōdo Shinshū. Rennyo is widely credited with the revival of the school and the establishment of the Honganji.a temple built around Shinran's mausoleum, as the undisputed head temple of the school. Although the eldest son of his father Zonnyo, Rennyo was actually illegitimate, and at first it appeared that the first son of Zonnyo's wife would succeed him as head of the Honganji. However, influential leaders within the school, recognizing Rennyo's talent, persuaded the school to accept Rennyo as the temple head. Rennyo then went on preaching tours to make converts and consolidate temple devotees in various areas, a task made difficult by the violent opposition of the Tendai headquarters at Mt. Hiei to the Honganji's growth. When this opposition eventuated in open, armed conflict, Rennyo chose to move the Honganji to safer grounds away from Mt. Hiei.
Rennyo was very successful in building up the Jōdo Shinshū membership because of his skill as a speaker, letter-writer, and diplomat. He spoke persuasively of the need for people in his troubled age to put their faith in the saving power of the Buddha Amitābha.and he wrote letters prolifically to local congregations resolving doubts, settling internal conflicts, and inspiring followers to greater faith. These letters, or ofumi, were written in very accessible vernacular and illustrated their points with memorable stories; they have been conserved and are still treasured as Shinshū classics to this day. Furthermore, when the peasant rebellions, called ikkō ikki broke out, he became a trusted mediator; the aristocrats appreciated his willingness to counsel non-violence (see ahiṃsā) and to expel those who advocated armed conflict from the Shinshū rolls, and the peasants felt he represented their grievances fairly to the landowning classes. At the time of his birth, the Jōdo Shinshū was a fragmented, struggling sect, and the Honganji was a dilapidated temple with no real influence or authority. By the time of his death, the school had achieved unity with the Honganji at its apex. These developments are widely credited to Rennyo, and the school thus acclaims him as its ‘second founder’.