This paper introduces a novel electromechanical energy conversion system, called Machine Integrated with Trans-Rotary Magnetic Gear (MITROMAG) as a force-dense linear motor/generator. The device is obtained by integrating a Trans-Rotary Magnetic Gear (TROMAG) into a 3-phase winding. The TROMAG converts a low speed high force linear motion of a translator to a low torque high speed rotation of a rotor. Upon adding Permanent Magnet (PM) poles to the outer surface of the rotor of the TROMAG, it also serves as the rotor of an inner rotor PM machine. The resultant electromechanical device is compared to a PM linear tubular machine, as a benchmark, for a given force and speed. Simplified analytical models along with accurate field solutions and Finite Element Analysis (FEA) are employed to design the systems. It is shown that, for the given design specifications, the MITROMAG would surpass the linear PM machine in regard to the volume and weight with a great margin.