The Arnoux system is a train articulation system, for turning on railroad tracks, invented by Jean-Claude-Républicain Arnoux and patented in France in 1838. Arnoux was the chief engineer of the Ligne de Sceaux, which was originally built with very tight radii in the area around Sceaux, Hauts-de-Seine.
With the support of the French Academy of Sciences, Arnoux devised a new articulation system that allowed train wheels to turn, the système ferroviaire dit Arnoux ("Arnoux rail system"), and the Ligne de Sceaux was built to test his prototypes. The line started commercial use in 1846, but the operating cost and the use of a broad gauge of 1,750 mm (5 ft 8+7⁄8 in) meant that it was not taken up more widely. The invention of the bogie made it redundant. It was abandoned entirely by 1893.