Cheng Yi (simplified Chinese: 程颐; traditional Chinese: 程頤; pinyin: Chéng Yí; Wade–Giles: Ch'eng I, 1033–1107), courtesy name Zhengshu (正叔), also known as Mr. Yichuan (伊川先生), was a Chinese philosopher born in Luoyang during the Song Dynasty. He worked with his older brother Cheng Hao (程顥). Like his brother, he was a student of Zhou Dunyi, a friend of Shao Yong, and a nephew of Zhang Zai.