A recoilless rifle, recoilless launcher or recoilless gun, sometimes abbreviated to "RR" or "RCL" (for ReCoilLess) is a type of lightweight artillery system or man-portable launcher that is designed to eject some form of countermass such as propellant gas from the rear of the weapon at the moment of firing, creating forward thrust that counteracts most of the weapon's recoil. This allows for the elimination of much of the heavy and bulky recoil-counteracting equipment of a conventional cannon as well as a thinner-walled barrel, and thus the launch of a relatively large projectile from a platform that would not be capable of handling the weight or recoil of a conventional gun of the same size. Technically, only devices that use spin-stabilized projectiles fired from a rifled barrel are recoilless rifles, while smoothbore variants (which can be fin-stabilized or unstabilized) are recoilless guns. This distinction is often lost, and both are often called recoilless rifles.

Though similar in appearance to a tube-based rocket launcher (since these also operate on a recoilless launch principle), the key difference is that recoilless weapons fire shells using a conventional smokeless propellant. While there are rocket-assisted rounds for recoilless weapons, they are still ejected from the barrel by the deflagration of a conventional propelling charge.

Because some projectile velocity is inevitably lost to the recoil compensation, recoilless rifles tend to have inferior range to traditional cannon, although with a far greater ease of transport, making them popular with paratroop, mountain warfare and special forces units, where portability is of particular concern, as well as with some light infantry and infantry fire support units. The greatly diminished recoil allows for devices that can be carried by individual infantrymen: heavier recoilless rifles are mounted on light tripods, wheeled light carriages, or small vehicles, and intended to be carried by crew of two to five. The largest versions retain enough bulk and recoil to be restricted to a towed mount or relatively heavy vehicle, but are still much lighter and more portable than cannon of the same scale. Such large systems have been replaced by guided anti-tank missiles in many armies.