The Prime Material Plane (also called the Material Plane, the Prime Material, or just the Prime) is the central plane of existence in the Dungeons & Dragons role-playing game. The Prime Material Plane is the primary location of most Dungeons & Dragons campaign settings, with the exceptions of Ravenloft and Planescape.
The inhabitants of each Material Plane always refer to their own plane as the Prime Material Plane.
In the cosmology shared by the Planescape and Spelljammer settings, there is only one Prime Material Plane, which contains many different worlds. In other cosmologies, such as that used by the Manual of the Planes, there are numerous different Material Planes. (The Third Edition Manual of the Planes refers exclusively to the "Material Plane" rather than the "Prime Material Plane".)
In the Planescape campaign setting, those persons coming to the extraplanar city of Sigil from the Prime are referred to as "primes" themselves. "Primes" are often treated as clueless inferiors by the planar elitists who dwell in Sigil and other planes.
In 4th Edition, the terms "Prime Material Plane" and "Material Plane" are no longer in use, the plane of existence on which adventures normally take place is known as the natural world.