The .44 Remington Magnum, also known as .44 Magnum or 10.9x33mmR, is a rimmed, large-bore cartridge originally designed for revolvers and quickly adopted for carbines and rifles. Despite the .44 designation, guns chambered for the .44 Magnum round, and its parent, the .44 Special, use 0.429 in (10.9 mm) diameter bullets. The .44 Magnum is based on the .44 Special case but lengthened and loaded to higher pressures for greater velocity and energy.

Famously called the most powerful handgun [cartridge] in the world by Clint Eastwood in Dirty Harry, the .44 Magnum has since been eclipsed in power by the .454 Casull, .460 S&W Magnum, .480 Ruger, .50 Action Express, and .500 S&W Magnum; nevertheless, due in part to more manageable recoil it has remained one of the most popular commercial large-bore magnum cartridges.