Brumaire, the name of the second month in the republican calendar which was established in France by a decree of the National Convention on the 5th of October in the year II. (1793), completed with regard to nomenclature by Fabre d'églantine, and promulgated in its new form on the 4th of Frimaire in the year II. (the 24th of November 1793). The month of Brumaire began on the day which corresponded, according to the year, to the 22nd or to the 23rd of October of the old calendar, and ended on the 20th or 21st of November, It was divided into "decades" like the other months of the republican calendar. Its name alludes to the fogs and mists frequent at that time of the year. The most important event in French history which took place during that month was the coup d'état of the 18th Brumaire in the year VIII. (the 9th of November 1799), by which General Bonaparte overthrew the government of the Directory to replace it by the Consulate.

On the republican calendar, see G. Villain, "Le Calendrier républicain," in La Révolution française for 1884-1885.