Camille Jordan (January 5 1838 - January 22 1921) was a French mathematician, known both for his foundational work in group theory and for his influential Cours d'analyse. He was born in Lyons and educated at the Ecole Polytechnique. He was an engineer by profession; later in life he taught at the Ecole Polytechnique and the College de France; where he had a reputation for eccentric choices of notation.

He is remembered now by name in a number of foundational results:

• the Jordan curve theorem, a topological result required in complex analysis;
• the Jordan normal form, and the Gauss-Jordan elimination method, in linear algebra;
• in mathematical analysis, Jordan content is an area measure that predates measure theory;
• in group theory the Jordan-Hölder theorem on composition series is a basic result.

In fact the work of Jordan did much to bring Galois theory into the mainstream. He also investigated the Mathieu groups, the first examples of sporadic groups. His Traité des substitutions, on permutation groups, was published in 1870.