The Institute of Mathematics "Simion Stoilow" of the Romanian Academy is a research institute in Bucharest, specialized in Mathematics. It was named after Simion Stoilow, who was its first director, in 1949. The Institute was closed down in April, 1975, by a decree of Nicolae Ceauєescu; it reopened in January 1990, in the immediate aftermath of the Romanian Revolution of 1989.

In April 2000, the Institute was nominated as a Centre of Excellence in Research, through a competition organized by the European Commission.

The Institute is located on Calea Grivitei, in central Bucharest.