Tsou Yen (active late 4th century BC) was a Chinese philosopher important for developing the so-called Five Element theory, fundamental to Chinese philosophy and science.

Tsou Yen was born in Ch'i, a state in modern Shantung Province, where the Tsou family had established a reputation for scholarship early in the 4th century B.C. During this time the rulers of Ch'i had become active supporters of scholarly activities, and they established at the Ch'i capital an academy known as Chi-hsia, which was attended by hundreds of scholars from all parts of China. Tsou Yen was one of the most distinguished of these scholars and was held in particularly high esteem by the ruling family of Ch'i.

Little is known of Tsou Yen's life. He apparently became a popular figure in several of the states outside of Ch'i. He traveled to the neighboring state of Wei, where the ruler...