Macroeconomics, as a field of study, doesn't have a single inventor. It evolved over time through contributions from various economists. However, John Maynard Keynes is often considered a key figure in the development of modern macroeconomics. His influential work, "The General Theory of Employment, Interest, and Money," published in 1936, laid the foundation for understanding aggregate economic phenomena and the role of government in stabilizing economies, especially during times of recession.