Rennyo (蓮如, 1415–1499) was the 8th Monshu (Patriarch) of the Hongan-ji Temple of the Jōdo Shinshū sect of Buddhism, and descendant of founder Shinran. Jodo Shinshu Buddhists often referred to him as the restorer of the sect (Chūkō no sō (中興の祖) in Japanese). He was also known as Shinshō-in (信証院), and posthumously Etō Daishi (慧灯大師). During the conflict and welter of the Ōnin War and the subsequent warfare (Sengoku era) that spread throughout Japan, Rennyo was able to unite most of the disparate factions of the Jodo Shinshu sect under the Hongan-ji, reform existing liturgy and practices, and broaden support among different classes of society. Through Rennyo's efforts, Jodo Shinshu grew to become the largest, most influential Buddhist sect in Japan.

Rennyo is venerated along with Shinran, and liturgical reforms he implemented are still in use today in Jodo Shinshu temples. Further, Rennyo's letters were compiled and are still recited in Jodo Shinshu liturgy.

Rennyo maintained a complex relationship with the Ikkō-ikki peasant revolts, which were frequently by Shinshu followers, restraining them at times while also teaching and attending to their religious needs.

Born as Hoteimaru (布袋丸), later Kenju (兼寿), Rennyo was the son of Zonnyō (存如, 1396–1457, who later became the 7th Monshu (門主; "Patriarch") of the Hongan-ji. Rennyo was born out of wedlock when his father was 18. His mother, a servant whose name is now unknown, was sent away when Rennyo was only six years old. Several times throughout his life he attempted to find her, with no result.

Rennyo frequently quarreled with his stepmother, Nyoen (d. 1460), and she attempted to have her own son, Ogen (1433–1503), installed as the successor to the abbacy of Hongan-ji. However, Rennyo's influential uncle, Nyojo (1402–1460), dismissed the idea and Rennyo ultimately succeeded as the 8th Monshu.

Following his installation as 8th head priest at Hongan-ji in 1457, Rennyo focused his efforts in proselytizing in Ōmi Province, an area dominated by the Bukkō-ji and Kinshoku-ji branches of Shinshū. Due to timely support from the Katada congregation, Rennyo was able to expand the Honganji's presence. These congregations in Omi Province were frequently composed of artisan-class followers, who were able to provide crucial funds and protection. During his early ministry, Rennyo would frequently distribute religious texts to congregations as well as inscriptions of the nenbutsu (recitation of Amitābha Buddha's name). These inscriptions frequently used the so-called "10-character nembutsu" or Jūjimyōgō (十字名号) :

Kimyō Jin Jippō Mugekō Nyorai
帰命尽十方無碍光如来

"I take refuge in the Tathāgata of Unobstructed Light Suffusing the Ten Directions".