thumb|200px|Henri Cazalis
Henri Cazalis (; 9 March 1840, Cormeilles-en-Parisis, Val-d'Oise – 1 July 1909, Geneva) was a French physician who was a symbolist poet and man of letters and wrote under the pseudonyms of Jean Caselli and Jean Lahor.
His works include:
- (1865)
- (1865)
- (1868)
- (1872)
- (1872)
- (1875-1893)
- (1885)
- (1896)
- (1897).
The author of the had a predilection for gloomy subjects and especially for pictures of death. His oriental habits of thought earned for him the title of the (cf. ).
Some of his poems have been set to music by Camille Saint-Saëns, Henri Duparc, Charles Bordes, Ernest Chausson, Reynaldo Hahn, Edouard Trémisot, Dagmar de Corval Rybner, and Paul Paray.
He also maintained a correspondence of interest with the poet Stéphane Mallarmé from 1862 to 1871.
See a notice by Paul Bourget in (1887–1888); Jules Lemaître, (1889); Émile Faguet in the (October 1893). George Santayana's Poetry and Religion (1900) has an essay on his concept of .
Saint-Saëns' ('Dance of Death') is based on this poem written by Henri Cazalis.