Agustín Guillermo Carstens Carstens (born in 1958 in Mexico City) is a Mexican economist and current Secretary of Finance in the cabinet of Felipe Calderón. Previously, he served as Deputy Managing Director of the International Monetary Fund from 1 August 2003 to 16 October 2006 and as Treasurer of the Bank of Mexico.

Carstens graduated with a bachelor's degree in Economics from the Autonomous Technological Institute of Mexico (ITAM)where he received the second place in Banamex`s Economics Tesis Award for the year 1982. After working as an intern in the Bank of Mexico he received a scholarship and completed both a master's degree (1983) and a doctorate in Economics (1985) at the University of Chicago. His thesis advisor was Michael Mussa, former Economic Counselor and Director of the Department of Research at the International Monetary Fund from 1991 to 2001, with whom he long kept a close relationship.

In the mid 1980s Carstens returned to Mexico and rejoined the central bank. Before turning 30 he was appointed Treasurer, effectively taking charge of the national reserves. Rising through the ranks in the early 1990s, he was appointed Chief of Staff of chairman Miguel Mancera, and was General Director of Economic Research at the end of the 1990's, in charge of designing the Bank's economic policy with governor Guillermo Ortiz Martínez in the aftermath of the Tequila Crisis and the Russian default crisis. He oversaw the creating of the 'Corto' mechanism with which the bank implemented monetary policy for the best part of a decade. While at the Bank he produced several research articles about the Mexican Economy and in particular, coauthored an analysis of the Mexican Crisis along with then Deputy Governor Francisco Gil Diaz which suggests the Mexican crisis was to a large extent an avoidable run on the Mexican peso brought about by external circumstances and political problems.