Dorwinion means Land of Wine and in the Third Age referred to a wine-growing area on the shores of the Sea of Rhun. Its exact location of is not indicated on any map but the area produced the strong wines enjoyed by the Elvenking in The Hobbit.

Tolkien at one time set an area of this name on the isle of Tol Eressea but abandoned this idea. In the Lays of Beleriand he mentions wines of Dorwinion, but again is not specific as to its location. In the first age the wines of Dorwinion were known to have been enjoyed in the Thousand Caves in Menegroth by King Thingol. So we can assume, that the wines were favoured by Elves throughout the Three Ages.
Encyclopedia entry originally written by PotbellyHairyfoot