Austrian-born American economist, writer, and educator whose major field of expertise was international trade.

Haberler studied economics at the University of Vienna under Friedrich von Wieser (Wieser, Friedrich von) and Ludwig von Mises (Mises, Ludwig von), receiving his doctorate in 1925. After further study in England and the United States, he taught economics and statistics at the University of Vienna from 1928 to 1936. He also served as consultant to the League of Nations during his last two years in Vienna. In 1936 he became a professor of economics at Harvard University, a post he held until 1971, when he joined the American Enterprise Institute in Washington, D.C.

Haberler became famous chiefly as a writer on international trade, and his major work, The Theory of International Trade (1937), is considered a classic. Particularly influential was his reformulation of the theory of comparative (comparative advantage) costs in terms of opportunity cost. He introduced the production substitution curve (now referred to as the production-possibility frontier), which offered a framework for considering the effects of multiple variables in the process of production. This led to major insights in the theory of international trade. Haberler also helped to revive the influence of the purchasing power parity doctrine, which states that relative price levels are major determinants of equilibrium exchange rates (exchange rate). He produced influential work on the flexibility and stability of exchange rates as well as on tariffs (tariff). Haberler was ahead of his time in advocating, in 1959, free trade as an effective policy for developing countries. His marked ability to synthesize the important elements in economic literature was also apparent in a classic study of business cycle theory that he wrote for the League of Nations, Prosperity and Depression (1937).