Risshū (律宗), also Ritsu-shu, is one of the six schools of Nara Buddhism in Japan, noted for its use of the Vinaya textual framework of the Dharmaguptaka, one of the early schools of Buddhism; Risshū is the Japanese term for Vinaya.
The Ritsu school was formally established in China during the Tang dynasty by Daoxuan, founder of the Nanshan Vinaya school. Daoxuan completed the scholastic system of Vinaya studies with his Commentary on the Four-Part Vinaya (四分律行事鈔). He belonged to the lineage of Huiguang (468–537), a disciple of the Dilun school, and trained prominent monks such as Wengang, Zhuxiu, Daoshi, and Hongjing.