Russell Cornell Leffingwell (1878-1960) was an American banker and economist, best known as a chairman of J.P. Morgan & Co. He played a significant role in international finance during the early 20th century, particularly in post-World War I European debt restructuring and monetary stabilization. A proponent of the gold standard and fiscal discipline, Leffingwell served as an advisor to the U.S. Treasury and influenced Federal Reserve policies. His career bridged Wall Street and public policy, leaving a mark on global economic governance.