For patients with physical or cognitive impairments, there is a pressing need to improve the recovery of their physical functions through specific therapeutic training processes. Thanks to its customization potential, Rehabilitation Robotics is becoming an essential area of Robotics for Medicine and Healthcare. This work concerns the design of a human-robot interaction module for gravity compensation to be used in robot-assisted rehabilitation of the hand and upper limb. The proposed module is designed to be connected, on one side, to a collaborative manipulator as an end-effector and, on the other side, to the patient’s forearm. The aim is to compensate for upper limb gravity during rehabilitation exercises while ensuring complete freedom of movement in the three-dimensional operating space. The perspective is to use the proposed solution as an enabling technology for more in-depth and targeted rehabilitation sessions once coupled with proper user-centred control strategies for the manipulator.