A Wollaston prism, inverted by William Hyde Wollaston, is an optical device that manipulates polarized light. It separates randomly polarized or non-polarized light into two orthogonal linearly polarized outgoing beams.

The Wollaston prism consists of two orthogonal calcite prisms, cemented together on their base to two right triangle prisms with perpendicular optic axes. The Wollaston prism is commonly used as a polarizing beam splitter. The deviation of the two transmitted beams are nearly symmetric about the incident beam direction. The polarization of the output beams are parallel and perpendicular to the plane where the entrance and exit beam lie. The beam splitting angle varies with the wavelength, therefore the data in the data table below are approximate.