Zhou Zuoren (Chinese: 周作人; pinyin: Zhōu Zuòrén; Wade–Giles: Chou Tso-jen) (16 January 1885-6 May 1967) was a Chinese writer, primarily known as an essayist and a translator. He was the younger brother of Lu Xun (Zhou Shuren), the second of three brothers.

Born in Shaoxing, Zhejiang, he was educated at the Jiangnan Naval Academy as a teenager. Following the steps of his brother Lu Xun, he left for Japan to pursue his studies in 1906. During his stint in Japan, he began studying Ancient Greek, with the aim of translating the Gospels into Classical Chinese, and attended lectures on Chinese philology by scholar-revolutionary Zhang Binglin at Rikkyo University, although he was supposed to study civil engineering there. He returned to China in 1911, with his Japanese wife, and began to teach in different institutions.

Writing essays in vernacular Chinese for the influential magazine La Jeunesse, Zhou was a key figure in the May Fourth Movement. He was an advocate of literary reform. In a 1918 article, he called for a "humanist literature" in which "any custom or rule that goes against human instincts and nature should be rejected or rectified". As examples, he cited children sacrificing themselves for their parents and wives being buried alive to accompany their dead husbands. Zhou's ideal literature was both democratic and individualistic. On the other hand, Zhou made a distinction between "democratic" and "popular" literature. Common people may understand the latter, but not the former. This implies a difference between common people and the elite.