The .45-70 cartridge is a type of centerfire rifle cartridge that was first introduced in 1873 for use in the Springfield Model 1873 "Trapdoor" rifle. It was originally designed as a black powder cartridge, but later versions have been adapted for smokeless powder.

The name of the cartridge comes from its bullet diameter of .45 inches (11.43 mm) and its original black powder charge of 70 grains (4.54 g).

The .45-70 cartridge typically uses a bullet that weighs between 300 and 500 grains (19.44 to 32.40 g) and has a muzzle velocity of around 1,300 to 1,400 feet per second (396 to 427 meters per second). The cartridge has a maximum effective range of around 1,500 yards (1,372 meters) when fired from a long-barreled rifle.

Today, the .45-70 cartridge is popular among hunters and shooters who enjoy the challenge of using traditional, big-bore rifles. It is often used for hunting large game such as elk, moose, and grizzly bear, as well as for target shooting and long-range shooting competitions.