Kenneth Joseph Arrow (August 23, 1921 – February 21, 2017) was an American economist, mathematician and political theorist. He received the John Bates Clark Medal in 1957, and the Nobel Memorial Prize in Economic Sciences in 1972, along with John Hicks.

In economics, Arrow was a major figure in postwar neoclassical economic theory. Four of his students (Roger Myerson, Eric Maskin, John Harsanyi, and Michael Spence) went on to become Nobel laureates themselves. His contributions to social choice theory, notably his "impossibility theorem", and his work on general equilibrium analysis are significant. His work in many other areas of economics, including endogenous growth theory and the economics of information, was also foundational.

Arrow was born on August 23, 1921, in New York City. Arrow's mother, Lilian (Greenberg), was from Iași, Romania, and his father, Harry Arrow, was from nearby Podu Iloaiei. The family was of Romanian-Jewish descent, and very supportive of Kenneth's education. Growing up during the Great Depression, he embraced socialism in his youth. He would later move away from socialism, but his views retained a left-leaning philosophy.

He graduated from Townsend Harris High School and then earned a bachelor's degree in mathematics from the City College of New York in 1940, where he was a member of Sigma Phi Epsilon. He then attended Columbia University for graduate studies, obtaining a master's degree in mathematics in June 1941. At Columbia, Arrow studied under Harold Hotelling, who influenced him to switch fields to economics. He served as a weather officer in the United States Army Air Forces from 1942 to 1946.

From 1946 to 1949 Arrow was a graduate student at Columbia, and also worked as a research associate at the Cowles Commission. During that time he also was an assistant professor of economics at the University of Chicago and worked at the RAND Corporation in California. He left Chicago to become an acting assistant professor of economics and statistics at Stanford University. In 1951, he earned his PhD from Columbia. He served in the government on the staff of the Council of Economic Advisers in the 1960s with Robert Solow. In 1968, he left Stanford for Harvard University, where he was appointed Professor of Economics; it was during his tenure there that he received the Nobel Prize in Economics.

Arrow returned to Stanford in 1979 and became the Joan Kenney Professor of Economics and Professor of Operations Research. He retired in 1991. As a Fulbright Distinguished Chair, in 1995 he taught economics at the University of Siena. He was also a founding member of the Pontifical Academy of Social Sciences and a member of the board at the Santa Fe Institute. At various stages in his career he was a Fellow of Churchill College, Cambridge. He was one of the founding editors of the Annual Review of Economics, which was first published in 2009.

Four of his former students have gone on to become Nobel Prize winners, namely John Harsanyi, Eric Maskin, Roger Myerson, and Michael Spence. A collection of Arrow's papers is housed at the Rubenstein Library at Duke University.

Arrow's monograph Social Choice and Individual Values derives from his 1951 PhD thesis.