American sociologist who employed a sociopsychological approach to the understanding of society.

Cooley, the son of Michigan Supreme Court judge Thomas McIntyre Cooley, earned his Ph.D. at the University of Michigan in 1894. He had started teaching at the university in 1892, became a full professor of sociology in 1907, and remained there until the end of his life.

Cooley believed that social reality was qualitatively different from physical reality and was therefore less amenable to measurement. Because of this view, he was more productive as a social theorist than as a research scientist. His Human Nature and the Social Order (1902, reprinted 1956) discussed the determination of the self through interaction with others. Cooley theorized that the sense of self is formed in two ways: by one's actual experiences and by what one imagines others' ideas of oneself to be—a phenomenon Cooley called the “looking glass self.” This dual conception contributed to Cooley's fundamental theory that the mind is social and that society is a mental construct.

In Social Organization (1909, reprinted 1956), Cooley outlined the objective consequences of his psychological views. He argued that the ideal of the moral unity of society, involving qualities of loyalty, justice, and freedom, was derived from face-to-face relationships in primary groups such as the family and neighbourhood or children's play groups. In his last major work, Social Process (1918, reprinted 1966), he applied the Darwinian (Darwinism) principles of natural selection and adaptation to collective (social) existence.