Single malt Scotch refers to single malt whisky made in Scotland. To qualify for this category, a whisky must have been distilled at a single distillery using a pot still distillation process and made from a mash of malted barley. Therefore, a single malt means that the whisky has not been blended elsewhere with whisky from other distilleries. As with any Scotch whisky, a single malt Scotch must be distilled in Scotland and matured in oak casks in Scotland for at least three years, although most single malts are matured longer.
- "Malt" indicates that the whisky is distilled from a "malted" barley. Malting calls for soaking the grains in water for several days until it germinates. Heat is then applied to stop the germination, often using peat as the fuel. Other grains, such as rye or wheat, can be malted for other types of whisky, but barley must be used for single malt Scotch. The dry malt is ground into flour (grist) and mixed with hot water; this mashing process converts the starch into sugar. Later, yeast is added to increase the process of fermentation. Finally, impurities such as methanol are removed during distillation; that also increases the alcohol content.
- "Single" indicates that all the spirits in the bottle come from a single distillery. That distillery may combine single malt whiskies of several ages in a bottle.
Until the Scotch Whisky Regulations 2009 (SWR 2009), the word "blended" only appeared (in the context of Scotch whisky) on bottles of whisky that contained a mixture of both barley and non-barley grain whisky, but this is no longer the case. Under the terminology established by the SWR 2009, the term "blended malt Scotch whisky" replaced the term "vatted malt" to describe a mixture of single malt Scotch whiskies (malted barley whisky).
Only about 10% of the Scotch whiskies on the market are defined as single malt. The other 90% is made by combining numerous whiskies, typically two-thirds grain whisky (non-barley) and one-third malt whisky, from several, or numerous, distilleries in Scotland. The resulting products are labeled "blended Scotch whisky", without the word "malt". Nearly 90% of Scotch whisky sold each year is a blended type. Nonetheless, in 2018, single malt Scotch made up nearly 28% of the £4.7 billion of whisky exported from Scotland.