The Rinzai school of Zen (臨済宗; Japanese: Rinzai-shū, Chinese: 临济宗 línjì zōng) is one of three sects of Zen in Japanese Buddhism (with Sōtō and Ōbaku).
Rinzai is the Japanese line of the Chinese Linji school, which was founded during the Tang Dynasty by Linji Yixuan (Japanese: Rinzai Gigen).
Though there were several attempts to establish Rinzai lines in Japan, it first took root in a lasting way through the efforts of the monk Myōan Eisai. In 1168, Myōan Eisai traveled to China, whereafter he studied Tendai for twenty years. In 1187, he went to China again, and returned to establish a Linji lineage, which is known in Japan as Rinzai. Decades later, Nanpo Shōmyō (南浦紹明) (1235–1308) also studied Linji teachings in China before founding the Japanese Ōtōkan lineage, the most influential and only surviving branch of Rinzai.
The time during which Rinzai Zen was established in Japan also saw the rise of the samurai to power. Along with early imperial support, Rinzai came to enjoy the patronage of this newly ascendant warrior class.