Casimir Lefaucheux (26 January 1802 – 9 August 1852) was a French gunsmith. He was born in Bonnétable and died in Paris.
Casimir Lefaucheux obtained his first patent in 1827. In 1832, he completed a drop-barrel sporting gun with paper-cased cartridges.
Casimir Lefaucheux is credited with the invention of one of the first efficient self-contained cartridge system in 1836, featuring a pin-fire mechanism. This followed the pioneering work of Jean Samuel Pauly in 1808-1812. The Lefaucheux cartridge had a conical bullet, a cardboard powder tube, and a copper base that incorporated a primer pellet. Lefaucheux thus proposed one of the first practical breech-loading weapons.
In 1846, the Lefaucheux system was improved upon by Benjamin Houllier, who introduced an entirely metallic cartridge of copper brass.
In 1858, the Lefaucheux pistolet-revolver became the first metallic-cartridge revolver to be adopted by a national government.
It is thought likely that the revolver with which Vincent van Gogh fatally shot himself in a field in 1890 was a 7mm Lefaucheux à broche; the pistol was found, extremely corroded, in about 1960 and is on display at the Van Gogh Museum in Amsterdam.
A 7mm Lefaucheux revolver used by Paul Verlaine to shoot and wound Arthur Rimbaud in 1873 became the highest priced firearm ever sold, as of 2016, with a price of €435,000 at a Paris auction.