We present the first X-ray spectrum of the active galaxy 3C 109 obtained with the Position Sensitive Proportional Counter on ROSAT. 3C 109 is one of the most intrinsically luminous sources within a redshift z=0.5, having a 0.1-2.4 keV luminosity of 5.6 X 10(45) erg s-1 which is comparable to that of 3C 273. The X-ray spectrum is affected by absorption in excess of the Galactic value derived froin H I observations, at a level in good agreement with the reddening implied by optical data. Although classified as a radio galaxy, the intrinsic properties of 3C 109 closely resemble those of luminous steep-spectrum radio quasars. Our result supports unification schemes for active galaxies which hypothesize that luminous radio galaxies and radio-loud quasars are the same population of objects viewed at different angles.