With the population of the world getting older and the working period becoming more extended, exoskeletons can be helpful to prevent occupational injuries and provide assistance for physically exhausting works. In this letter, a novel compact passive exoskeleton able to assist the elderly and workers with overhead tasks is introduced. The exoskeleton consists of a spherical shoulder mechanism and a variable stiffness mechanism, the latter being used to compensate torques due to gravity force. Numerical, analytical, and experimental analyses of the variable stiffness mechanism are carried out and compared. Topology optimisation is used to reduce the mass of the device. The final design, able to compensate for 50% of the gravitational torque of the arm with the elbow stretched, was tested and validated experimentally.