Russian-born American economist who has been called the father of input-output analysis (input–output analysis) in econometrics and who won the Nobel Prize for Economics in 1973.

Leontief was a student at the University of Leningrad (1921–25) and the University of Berlin (1925–28). He immigrated to the United States in 1931, teaching at Harvard University, Cambridge, Massachusetts, from 1931 to 1975. From 1948 to 1975 he was director of the Harvard Economic Research Project on the Structure of the American Economy. From 1975 until his death he was a professor of economics at New York University; he was named director of the school's Institute for Economic Analysis in 1978.

The core of his complex input-output system is a gridlike table showing what individual industries buy from and sell to one another. With the addition of government, consumers, foreign countries, and other elements, there emerges a general outline of the goods and services circulating in a national economy. The input-output method of economic analysis is used in various forms by a large number of industrialized countries for both planning and forecasting.

Leontief is also distinguished for having developed linear programming, a mathematical technique for solving complex problems of economic operations. He also is known for the “Leontief Paradox.” Economists had previously held that a country's exports reflect the commodity most abundant in that country—i.e., labour or capital. However, as Leontief pointed out, though the United States has more capital than most other nations, the majority of its exports were of labour-intensive goods; conversely, the majority of U.S. imports were of capital-intensive goods. This phenomenon came to be known as the Leontief Paradox.

His major publications are The Structure of the American Economy 1919–1929: An Empirical Application of Equilibrium Analysis (1941) and Input-Output Economics, 2nd ed. (1986).