This paper describes a polarimeter for use at wavelengths near 1 mm, designed to be self-contained and portable. Only minor modifications should be required to adapt this instrument for use on any of several millimeter and submillimeter telescopes. The polarimeter system and data-taking techniques are described, and a preliminary measurement is reported of the polarized dust emission from the Orion KL region at 1.3 mm using the NRAO 12 m telescope. The results are similar to previous polarization measurements of Orion at far-infrared and submillimeter wavelengths. The magnetic field direction implied by the polarization position angle is parallel to that found in the surrounding Orion region using optical and near- to midinfrared polarimetric techniques.