Geneviève de Brabant is an opéra bouffe, or operetta, by Jacques Offenbach, first performed in Paris in 1859. The plot is based on the medieval legend of Genevieve of Brabant.

For the 1867 version a comic duet for bass and baritone in the character of two gendarmes was added to Act 2: "Couplets des deux hommes d'armes". In English-speaking countries it is widely known as the "Gendarmes' Duet" or the "bold gendarmes", from H. B. Farnie's English adaptation. As well as being a popular performance-piece, it formed the basis for the U.S. "Marines' Hymn".

The two-act French libretto was written by Louis-Adolphe Jaime and Etienne Tréfeu, and the opera was first staged at the Théâtre des Bouffes Parisiens, Paris on 19 November 1859. A new three-act version (in which the Gendarmes' Duet first appeared), revised by Hector-Jonathan Crémieux, was first given at the Théâtre des Menus-Plaisirs, Paris, on 26 December 1867. An expanded five-act version was devised for a production at the Théâtre de la Gaîté on 25 February 1875. A Paris revival in 1908 at the Théâtre des Variétés with Geneviève Vix in the title role ran for 58 nights.

Geneviève de Brabant was first performed in Vienna (Die schöne Magellone) and Berlin in 1861 and Brussels and Madrid in 1869.

The New York premiere was on 22 October 1868, and Farnie's version was first seen in London at the Philharmonic Theatre in Islington, produced by and starring Emily Soldene as Drogan, with Selina Dolaro in the title role, on 11 November 1871. The production ran for a year and a half, and revivals took place over the following decade with Soldene repeating her Drogan.