Xavier Henry Napoleón Leroux (October 11, 1863, Velletri – February 2, 1919, Paris) was a French composer.
Leroux was the son of a military bandleader. He studied at the Paris Conservatory under Jules Massenet and Théodore Dubois, and won the Prix de Rome in 1885 with the cantata Endymion. From 1896 he taught harmony there. Notable students include Marc Delmas, Paul Paray, Roger Désormière, Eugène Bigot, Georges Dandelot, Albert Wolff, Henri Mulet and Louis Fourestier.
Leroux composed several orchestral and choral works, songs, and piano pieces, but he was primarily known for his operas.
- The Persians, Aeschylus
- Plutus, Aristophanes
- Evangéline, libretto by Louis de Gramont, 1895
- Astarté, libretto by Louis de Gramont, 1901
- La reine Fiammette, 1903
- Vénus et Adonis, libretto by Louis de Gramont, 1905
- William Ratcliff, libretto by Louis de Gramont after Heinrich Heine, 1906
- Le chemineau, 1907
- Théodora, 1907
- Le carillonneur, 1913
- La fille de Figaro, 1914
- Les cadeaux de Noël, 1915
- 1814, 1918
- Nausithoé, 1920
- La plus forte, 1924
- L'ingénu, 1931
- Hymne, 1914