Which economist is most associated with monetarism?

Milton Friedman is the economist most associated with monetarism.

Monetarism emphasizes the role of the money supply in determining economic activity and the price level. Friedman revived and modernized the quantity theory of money, arguing that monetary policy has powerful effects on output in the short run and inflation over longer periods. He generally favored predictable money-supply growth over discretionary attempts to fine-tune the economy.

Friedman’s influence grew in the 1950s and 1960s as he challenged Keynesian approaches centered on fiscal policy. His 1963 book, A Monetary History of the United States, co-written with Anna Schwartz, argued that monetary contraction greatly worsened the Great Depression. Monetarism became especially influential during the inflation debates of the 1970s, although direct money-supply targeting later lost favor as the relationship between monetary aggregates and prices proved unstable. A common mix-up is treating monetarism as the claim that money is the only economic influence; its distinctive emphasis is monetary policy’s central role.