Julien Koszul (4 December 1844 – 15 January 1927) was a French composer and pipe organist from Alsace.

[1] Born in Morschwiller-le-Bas, Alsace, Koszul studied at the École Niedermeyer de Paris with Camille Saint-Saëns, together with Gabriel Fauré and Eugène Gigout as fellow students and friends.

He encouraged Albert Roussel to undertake an artistic career.

Composer Henri Dutilleux and mathematician Jean-Louis Koszul were his grandsons.

Henri Dutilleux, who often recalled his memory, paid tribute to him in 2005 by being the originator of the publication of his correspondence.