Who is considered to be the most influential economist in the 20th century?

John Maynard Keynes is often regarded as the most influential economist of the 20th century. His ideas, particularly those articulated in "The General Theory of Employment, Interest, and Money" (1936), revolutionized economic thought by advocating for government intervention in the economy to manage demand and reduce unemployment. Keynesian economics laid the foundation for modern macroeconomic policy and significantly influenced economic practices during and after the Great Depression. His legacy continues to impact economic theory and policy today.