This paper proposes a mm-wave low-profile reflection polarizer based on single layer anisotropic impedance surfaces. It is demonstrated that by virtue of anisotropy it is possible to independently control the reflection characteristics of the two orthogonal components of a linearly-polarized incident plane waves and therefore achieve polarization conversion. A W-band prototype has been designed and its performance characteristics are evaluated. The 1.5 dB axial ratio relative bandwidth exceeds 51 %, while low loss and better than previously reported angular stability are also demonstrated. The structure is compatible with traditional PCB etching techniques and does not require stacking of multiple layers.