Saitō Masaru (斎藤 賢, January 24, 1868 - April 13, 1904), better known by his pen name Saitō Ryokuu (斎藤 緑雨), was a Japanese author and critic who lived during the Meiji Era.
In 1896, with Mori Ōgai (森 鷗外) and Kōda Rohan (幸田 露伴), Ryokuu started a literary journal, Mezamashi gusa (めさまし草) in which Takekurabe (たけくらべ) by Higuchi Ichiyō (樋口 一葉 ) was met with high critical acclaim. After Ichiyō died on November of this year, Ryokuu helped her mother and sister make a living although he was far from well-off. His literary friends include Kōtoku Shūsui (幸徳 秋水), Baba Kochō (馬場 孤蝶) and Yosano Tekkan (与謝野 鉄幹).
In 1904, tuberculosis, which had plagued Ryokuu for years worsened and no medical care helped him recuperate. On his deathbed, he referred Ichiyō's diaries which he had hoped to publish to Kochō and asked him to take dictation to prepare his own death notice. He died in the morning of April 13 of the same year.
Ryokuu was a distinguished aphorist as well as one of the most outspoken critics. Collections of his aphorisms were published in the late 20th century.