Noble rot is the name given to the benevolent form of a grey fungus, Botrytis cinerea, affecting wine grapes. Infestation by Botrytis requires moist conditions, and if the weather stays wet, the malevolent form, grey rot, can destroy crops of grapes. Grapes infected with Botrytis when they are ripe, but then exposed to drier conditions become partially raisined, and this form of infection is known as noble rot. Picked at a certain point during infestation can produce particularly fine sweet wine. Some of the finest Botrytized wines are literally picked berry by berry in successive tries (French for "pickings").
The best known fine wines made from noble rot infested grapes are Sauternes (France) and Tokaji (Hungary). Others include the Italian Amarone (although depending on conditions the grapes may be only minimally botrytized) and the German beerenauslese and trockenbeerenauslese. Noble rot has also been imported for use in artificial inoculation by winemakers in California and Australia.