Viosinho is a white Portuguese wine grape variety that is grown primarily in northern Portugal where it attains high acidity levels. It is primarily found in the Trás-os-Montes and Douro DOCs.J. Robinson Jancis Robinson's Guide to Wine Grapes pg 198 Oxford University Press 1996 It is used primarily as a blending grape where it adds structures and flavor to both still and fortified Port wines.Oz Clarke Encyclopedia of Grapes pg 284 Harcourt Books 2001

See also List of Port wine grapes

References