Abstract: Disclosed is a wrench that grips the internal surface of a pipe to be turned. When torque is applied to the wrench, one or more gripping surfaces are forced apart by a cam mechanism. The gripping surfaces tightly engage the internal surface of the pipe in response to movement of an internal cam. Torque applied to the wrench causes the pipe to turn. Because the wrench grips the internal diameter of a pipe, it can be used without damaging the external surface of the pipe, and used in very confined spaces. The gripping surfaces distribute the gripping load evenly across the pipe, which minimizes any deformation of the pipe.