Milton Friedman ( (listen); July 31, 1912 – November 16, 2006) was an American economist and statistician who received the 1976 Nobel Memorial Prize in Economic Sciences for his research on consumption analysis, monetary history and theory and the complexity of stabilization policy. With George Stigler and others, Friedman was among the intellectual leaders of the Chicago school of economics, a neoclassical school of economic thought associated with the work of the faculty at the University of Chicago that rejected Keynesianism in favor of monetarism until the mid-1970s, when it turned to new classical macroeconomics heavily based on the concept of rational expectations. Several students, young professors and academics who were recruited or mentored by Friedman at Chicago went on to become leading economists, including Gary Becker, Robert Fogel, Thomas Sowell and Robert Lucas Jr.

Friedman's challenges to what he called "naive Keynesian theory" began with his interpretation of consumption, which tracks how consumers spend. He introduced a theory which would later become part of the mainstream and among the first to propagate the theory of consumption smoothing. During the 1960s, he became the main advocate opposing Keynesian government policies, and described his approach (along with mainstream economics) as using "Keynesian language and apparatus" yet rejecting its initial conclusions. He theorized that there existed a natural rate of unemployment and argued that unemployment below this rate would cause inflation to accelerate. He argued that the Phillips curve was in the long run vertical at the "natural rate" and predicted what would come to be known as stagflation. Friedman promoted a macroeconomic viewpoint known as monetarism and argued that a steady, small expansion of the money supply was the preferred policy, as compared to rapid, and unexpected changes. His ideas concerning monetary policy, taxation, privatization and deregulation influenced government policies, especially during the 1980s. His monetary theory influenced the Federal Reserve's monetary policy in response to the global financial crisis of 2007–2008.

After retiring from the University of Chicago in 1977, and becoming Emeritus professor in economics in 1983, Friedman was an advisor to Republican President Ronald Reagan and Conservative British Prime Minister Margaret Thatcher. His political philosophy extolled the virtues of a free market economic system with minimal government intervention in social matters. He once stated that his role in eliminating conscription in the United States was his proudest achievement. In his 1962 book Capitalism and Freedom, Friedman advocated policies such as a volunteer military, freely floating exchange rates, abolition of medical licenses, a negative income tax, school vouchers and opposition to the war on drugs and support for drug liberalization policies. His support for school choice led him to found the Friedman Foundation for Educational Choice, later renamed EdChoice.

Friedman's works cover a broad range of economic topics and public policy issues. His books and essays have had global influence, including in former communist states. A 2011 survey of economists commissioned by the EJW ranked Friedman as the second-most popular economist of the 20th century, following only John Maynard Keynes. Upon his death, The Economist described him as "the most influential economist of the second half of the 20th century ... possibly of all of it".