Louis Nicolas (active 1667‒75) was a French Jesuit who in 1664 was sent to Canada as a missionary, where he remained until 1675. He traveled widely and developed a keen interest in the people, languages, flora, and fauna of New France. He wrote three major works, none of which was published in his lifetime but which survived in manuscript form: Histoire naturelle ou la fidelle recherche de tout ce qu'il y a de rare dans les Indes Occidantalles (Natural history, or the faithful research on all that is rare in the West Indies),known as Histoire Naturelle des Indes Occidentales (Natural history of the West Indies); the pictorial manuscript known as the Codex Canadensis; and Grammaire algonquine ou des sauvages de l'Amérique septentrionale (Algonquin grammar or on the natives of North America). The natural history, presented here, represents, according to its author, more than “20 years of assiduous work.” Its 12 books describe with equal quality and depth the fauna and flora of “a nearly infinite land” stretching from the land of the Eskimos to that of the Sioux. As is known from the introductory remarks to his Algonquin grammar, Nicolas conceived of the natural history as part of great work on New France, covering language, the topography of the New World, including a natural history of its plant and animal life, and the politics, customs, and religion of the natives. Nicolas returned to France in 1675 and was released from the Jesuit order in December 1678, although he remained a priest. Nothing is known of his subsequent life or when and where he died.