The .45 Remington–Thompson (11.4x25mm) was an experimental firearms cartridge designed by Remington Arms and Auto Ordnance for the Model 1923 Thompson submachine gun, a variant of the Model 1921 with a longer barrel, with the intent of increasing the power and range of the weapon.

[2][4] While some variants of the 1923 were produced, the rifle and round did not find commercial success.

[4]