Yes, the sweetness in sweet wines is completely natural. Despite the fact that the sweetness of some wines is manipulated during the fermentation process, no artificial sweetener is added to the wine.  As we mentioned above, all grapes that are used to make wine contain a certain amount of natural sugars. It is this sugar that converts into alcohol when the grapes are fermented. When the fermentation process is cut short, some of the natural sugars remain in the wine. It is these sugars that bring the sweetness to the wine.  We also mentioned fortified wines above which have additional alcohol in them. Despite the fermentation process being artificially shortened through the addition of an alcoholic substance, the sweetness of the wine is entirely natural. The addition of alcohol stops the fermentation process and allows a larger percentage of the natural sugars to remain in the wine.