Christopher A. Sims is an American econometrician and macroeconomist. He is currently the John F. Sherrerd ’52 University Professor of Economics at Princeton University. Together with Thomas Sargent, he won the Nobel Memorial Prize in Economic Sciences in 2011. The award cited their "empirical research on cause and effect in the macroeconomy".

Sims earned his A.B. in mathematics from Harvard University magna cum laude in 1963 and his PhD in Economics from Harvard in 1968. He has held teaching positions at Harvard, University of Minnesota, Yale University and, since 1999, Princeton. Sims is a Fellow of the Econometric Society (since 1974), a member of the American Academy of Arts and Sciences (since 1988) and a member of the National Academy of Sciences (since 1989). In 1995 he was president of the Econometric Society; in 2012, he was president of the American Economic Association.

Sims has published numerous important papers in his areas of research: econometrics and macroeconomic theory and policy. Among other things, he was one of the main promoters of the use of vector autoregression in empirical macroeconomics. He has also advocated Bayesian statistics, arguing for its power in formulating and evaluating economic policies.

Sims has been an outspoken opponent of the rational expectations revolution in macroeconomics, arguing that it should be thought of as a "cautionary footnote" to econometric policy analysis, rather than "a deep objection to its foundations." He has been similarly skeptical of the value of real business cycle models.

He also helped develop the fiscal theory of the price level and the theory of rational inattention.