Isabelle Gallagher (born 27 October 1973) is a French mathematician.

Her dissertation, supervised by Jean-Yves Chemin, concerned fluid dynamics.

[4] She worked at the French Centre national de la recherche scientifique and then, in 2004, became a professor at Paris Diderot University.

[1] She was elected president of the Société mathématique de France in june 2024.

In 2008, the French Academy of Sciences awarded her the Prix Paul Doistau–Émile Blutet.