Obstfeld, a professor at the University of California, Berkeley, will replace outgoing IMF economist Olivier Blanchard.
"His outstanding academic credentials and extensive international experience make him exceptionally well-placed to provide intellectual leadership to the IMF at this important juncture," said the Fund's managing director, Christine Lagarde, in a statement.
"He is known around the globe for his work on international economics and is considered one of the most influential macroeconomists in the world."
Obstfeld, 63, has been on leave from Berkeley since mid-2014 to serve on the White House Council of Economic Advisers.
