Léon Denis (January 1, 1846 – March 12, 1927) was a notable French spiritist philosopher,[1] and, with Gabriel Delanne and Camille Flammarion, one of the principal exponents of spiritism after the death of Allan Kardec.

Denis lectured throughout Europe at international conferences of spiritism and spiritualism, promoting the idea of survival of the soul after death and the implications of this for human relations.

"[citation needed] Denis was not just a successor to Allan Kardec, as is generally supposed, but was an important figure in consolidating the spiritist movement.

Possessing great moral sensibility, he dedicated his entire existence to the defense of the postulates that Kardec had transmitted in the books of the spiritist Pentateuch.

Denis himself summarized his mission as follows: "I have consecrated this existence to the service of a Great cause, Spiritism or Modern Spiritualism that will certainly be the universal faith, and the religion of the future.