Kosugi Tengai (小杉天外, November 7, 1865 – September 1, 1952) was the pen-name of a novelist in Meiji, Taishō and Shōwa period Japan. His real name was Kosugi Tamezō. He is considered the founder of the naturalism movement in modern Japanese literature. He was hired by the literary magazine Shincho gekan in 1897, but was transferred by the magazine to the newspaper Hōchi Shimbun. Kosugi was elected to the Japan Art Academy in 1948. In his later years, he also turned towards the genre of historical fiction. His grave is at the sub-temple of Myōkō-in, at Kenchō-ji in Kamakura.