The .50-70 Government, also known as the .50-70 Musket, .50-70 Springfield, and .50-1+3⁄4" Sharps) is a black powder cartridge adopted in 1866 for the Springfield Model 1866 trapdoor rifle.

The Springfield Model 1866 was the second iteration of the Allin-designed trapdoor breech-loading mechanism. Originally developed as a means of converting rifle muskets to breechloaders, the Allin modification ultimately became the basis for the definitive Springfield Model 1873, the first breech-loading rifle adopted by the United States War Department for manufacture and widespread issue to U.S. troops.