Single Malt Whisky must be produced entirely from a mash containing only malted barley, yeast and water. The entire production process must occur at a single distillery, including distillation, aging and bottling.
Single Malt Whiskies can however contain a mix of whiskies of different ages, brands do this to balance the flavours of younger spirits with the complexity of older whiskies. If any age statements are printed on the label, that is of the youngest spirit in a bottle.
A popular style amongst Scottish distillers, but also common in Japanese and Australian whisky. Single malt whiskies are often the most prized style of whisky produced by a distillery.