The Mismeasure of Man is a 1981 book by paleontologist Stephen Jay Gould. The book is both a history and critique of the statistical methods and cultural motivations underlying biological determinism, the belief that "the social and economic differences between human groups—primarily races, classes, and sexes—arise from inherited, inborn distinctions and that society, in this sense, is an accurate reflection of biology".

Gould argues that the primary assumption underlying biological determinism is that "worth can be assigned to individuals and groups by measuring intelligence as a single quantity". Biological determinism is analyzed in discussions of craniometry and psychological testing, the two principal methods used to measure intelligence as a single quantity. According to Gould, these methods possess two deep fallacies. The first fallacy is reification, which is "our tendency to convert abstract concepts into entities". Examples of reification include the intelligence quotient (IQ) and the general intelligence factor (g factor), which have been the cornerstones of much research into human intelligence. The second fallacy is that of "ranking", which is the "propensity for ordering complex variation as a gradual ascending scale".

The book received many positive reviews in the literary and popular press, while scientific reception was highly polarized. Positive reviews focused on the book's critique of scientific racism, the concept of general intelligence, and biological determinism, while critics accused Gould of historical inaccuracy, unclear reasoning, or political bias. The Mismeasure of Man won the National Book Critics Circle award. Gould's findings about how 19th-century researcher Samuel George Morton measured skull volumes were particularly controversial, inspiring several studies debating his claims.

In 1996, a second edition was released. It included two additional chapters critiquing Richard Herrnstein and Charles Murray's book The Bell Curve (1994).