The story
Founded by Charles Marpon and Ernest Flammarion in 1875, in Paris.1
Ernest Flammarion successfully launched his family publishing venture in 1875 with the Treaty of Popular Astronomy of his brother, astronomer Camille Flammarion. The firm published Émile Zola, Maupassant, and Jules Renard, as well as Hector Malot, Colette, and a wide list of medical, scientific, geographical, historical works as well as various autobiographies, including also the Père Castor children's series.
One of its early commercial successes was Édouard Drumont's virulent antisemitic tract La France juive ("Jewish France"), which Flammarion published in 1886 and reissued several times. During the Nazi occupation it reissued the book as recently as 1943.
From Wikipedia’s article on Groupe Flammarion, shared under CC BY-SA 4.0.4