Nicolas Camille Flammarion, Commandeur-Légion d'honneur (26 February 1842—3 June 1925) was a French astronomer and author. He was a prolific author of more than fifty titles, including popular science works about astronomy, several notable early science fiction novels, and several works about Spiritism and related topics. At the age of nineteen, he published his first work, La Pluralité des Mondes Habités, which caught the public taste and was at once translated into several languages. From 1862 to 1866 he was attached to the Bureau des Longitudes. He also published the magazine L'Astronomie, starting in 1882. He maintained a private observatory at Juvisy-sur-Orge, France.

Flammarion's La planète Mars et ses conditions d’habitabilité (1882) was taken up by Percival Lowell at the genesis of his quest to prove the existence of canals on Mars. Flammarion was a proponent of the notion of Martian canals, and he re-ran the 1903 Maunder experiment, using patterned discs copied at a distance by schoolboys, to determine if the appearance of canals could be an optical illusion. It was generally understood, and highlighted by Lowell afterwards, that Flammarion's results did not show canals to be a result of optical illusion. Flammarion's assistant, E.M. Antoniadi, who had disabused himself of the notion of canals through careful study, commented in the Journal of the RASC in 1933 that some of Flammarion's subjects did draw canals where there were none.

The asteroid (1021) Flammario is named for M. Flammarion. (107) Camilla, discovered by N. R. Pogson on November 17, 1868, was named after Camilla, Queen of the Volsci in Roman mythology... but it is believed by some that Camilla also derives from M. Flammarion's first name.

M. Flammarion was elected an Honorary Fellow of the Astronomical Society of Toronto on 1901-09-03. At the same meeting, president G.E. Lumsden announced that it was proposed to name a point in Lake Rosseau in the Muskoka region in honor of M. Flammarion, and the dedication has stuck.

Flammarion had written to the Society in thanks for his nomination, in a letter that was translated and published by the TAS:

Observatory of Juvisy, August 20, 1901.

Dear and Eminent Colleague,

I have been so absorbed, of late, preparing my second volume on the planet Mars, in the work of my observatory, and of the Astronomical Society of France, that my correspondence is much in arrears, and, for that reason, I must ask you to excuse any delay that has occurred in acknowledging your letter.