"Le Boudin" (French pronunciation: [lə budɛ̃]), officially "Marche de la Légion Étrangère" (English "March of the Foreign Legion"), is the official march of the French Foreign Legion. "Le Boudin" is a reference to boudin, a type of blood sausage or black pudding. Le boudin colloquially meant the gear (rolled up in a blanket) that used to be carried atop the backpacks of Legionnaires.
While the tune was composed prior to the Legion's departure for Mexico in the 1860s the lyrics were progressively composed after the Franco-Prussian War, since Alsatians and Lorrains flocked to the legion after these regions were annexed by Germany. The song makes also repeated reference to the fact that the Belgians are "lazy shirkers", this comes from the fact that the King of the Belgians, who wished to remain neutral in the Franco-German conflict, asked the French government to not commit the Belgian Legionnaires into the conflict. France agreed to this request and the Belgian Legionnaires remained in French Algeria (the Legion's home), to the dismay of the rest of the Legionnaires. This is why the song says that there's no blood sausage (boudin) for the Belgians. The song also mentions the Swiss who constituted the most important foreign contingent of the Legion in the 1870s.
"Le Boudin" is sung while standing to attention or marching by all ranks of the French Foreign Legion. The Legion marches at only 88 steps per minute, much slower than the 120 steps per minute of all other French military units. Consequently, the Legion contingent at the Bastille Day military parade march brings up the rear. Nevertheless, the Legion gets the most enthusiastic response from the crowd.
- The song is sung by the depleted half-company of Legionnaires in PC Wren's classic novel Beau Geste when the tiny garrison fool the besieging Tauregs into thinking that they are still at full strength. The Hollywood versions of Beau Geste don't include this vital part of the story, but the 1982 mini-series by the BBC stays true to the book and shows the soldiers singing the song.
- The 1978 film March or Die also features legionnaires singing the song, at the command of their officer Major Foster, played by Gene Hackman.
- The song also appears in the 1998 film Legionnaire starring Jean-Claude Van Damme, though in this film the soldiers don't sing the song to its traditional tune.
- Fabienne Fischer, Alsaciens Et Lorrains En Algerie: Histoire D'Une Migration, 1830-1914, p.120 
- "Foreign Legion July 14, 2012". YouTube. 2012-07-14. Retrieved 2015-04-24.
- "Beau Geste BBC 1982 EP 7 - The Battle - Le Boudin". YouTube. Retrieved 2015-04-24.
Le Boudin is sung at 18:40
- "Major Foster orders the singing of "Le Boudin"". YouTube (in French). Retrieved 2015-04-26.
- "La Legion" (in French). Retrieved 2015-04-24.
Le Boudin is sung twice in the first 2:05