The 21ème Regiment d'Infanterie is one of the oldest regiments in the World. It was raised in Lorraine in 1598 by Henri de Vaubecourt at the time when Henri of Navarre became King Henry IV of France. It continued as a regiment of the Monarchy under the name of its Colonel until it became the Regiment Guyenne in 1762.

It was not until the French Revolution that it was known as the 21eme Demi-Brigade de Ligne. The regiment served in Germany in 1793 and by the mid 1790's was in the Armme d'Italie. The 2leme was involved in action at Laona in 1796 and also Montenotee, Millesimo, Dego and the bridge at Lodi. It was at Lodi where Grenadiers of the Regiment charged over the bridge under constant fire shouting "Vive la Republique!" overthrowing the Austrian defenders and capturing their artillery.

In 1799 the regiment saw further action at Verona, Magano, Trebbia and most notably the Battle of Novi. It was here that Sergeant-Major Jean Georges Pauly, cut off by a body of Russian Cavalry was called upon to surrender. Replying Je Passe Quand Même he rallied a handful of men and forced his way back to the regiment using musket butt and bayonet killing or wounding more than 40 Russians in the process.

The regiment was designated the 21eme Regiment d' Infanterie de Ligne in 1803. In 1804 it formed part of the Armee d' Angleterre when the concept of the Grande Armee was first created by Napoleon Bonaparte. In 1805 the regiment marched under Marshal Louis Nicoholas Davout as part of the 3eme Corp d' Armee to fight the combined might of Austria and Russia at Austerlitz.

In 1806 Davout's Corps found itself facing the main Prussian army under the Duke of Brunswick at Auerstadt, whilst Napoleon was defeating what he believed to be the main army at Jena. The 21eme defended the village of Hassenhausen in the centre of the French line. Corporal Boutloup of the Voltigeur company, along with six men, took a Prussian gun and caisson and turned it on the Prussians.