Louis-Sébastien Mercier (6 June 1740 – 25 April 1814) was a French dramatist and writer, whose 1771 novel L'An 2440 is an example of proto-science fiction.

Early on, he came to the conclusion that Boileau and Racine had ruined the French language and that the true poet wrote in prose.

Mercier's keen observations on his surroundings and the journalistic feel of his writing meant that his work remained riveting despite the nature of its composition.

"There is no better writer to consult," Robert Darnton writes, "if one wants to get some idea of how Paris looked, sounded, smelled, and felt on the eve of the Revolution.

"[1] The most important of his miscellaneous works are L'An 2440, rêve s'il en fut jamais (1771), L'Essai sur l'art dramatique (1773), Néologie ou Vocabulaire (1801), Le Tableau de Paris (1781–1788), Le nouveau Paris (1799), Histoire de France (1802) and Satire contre Racine et Boileau (1808).

He decried French tragedy as a caricature of antique and foreign customs in bombastic verse and advocated the drame as understood by Diderot.

He denied that modern science had made any real advances; in a jesting passage, he even carried his conservatism so far as to maintain that the earth was a circular flat plane around which revolved the sun.

Mercier was a Freemason and member of the Lodge of Nine Sisters; a board (or, as it is known in French, a planche)—an official document laying out Mercier's perspective as a member of this Masonic lodge, states the following in French: I have sometimes said to myself, if of all the stirring books in the world there were only one left, what a language there would be in this book, with all its accessories, as well as it as speech, though it would be mute!