A Boule de Moulins was a method of transporting mail from the provinces to the city of Paris, used during the siege of the 1870 war. As the mail to be transported in this way in hollow spheres is first centralized in Moulins (Allier), these balls are called "de Moulins".

The siege of Paris took place from 19 September 1870 to 28 January 1871 and ended in the capture of the city by forces of the various states of the North German Confederation, led by the Kingdom of Prussia. The siege was the culmination of the Franco-Prussian War, which saw the Second French Empire attempt to reassert its dominance over continental Europe by declaring war on the North German Confederation. The Prussian-dominated North German Confederation had recently emerged victorious in the Austro-Prussian War of 1866, which led to the questioning of France's status as the dominant power of continental Europe. With a declaration of war by the French parliament on 16 July 1870, Imperial France soon faced a series of defeats at German hands over the following months, leading to the Battle of Sedan, which, on 2 September 1870, saw a decisive defeat of French forces and the capture of the French emperor, Napoleon III.