Pronounced mahr-sahn. A grape varietal, used in the production of white wine, originating in the Rhône region of France. The grape is also grown in Australia, Switzerland, and the United States. Austria and Australia produce Marsanne as a 100% varietal. It is a blending partner of Roussanne and Viognier, and the primary white wine varietal used in the production of Crozes-Hermitage, Saint Joseph, and Hermitage (high quality white wines). Marsanne is also sanctioned as a varietal for Hermitage reds.