Lambic is a very distinctive style of beer brewed only in the Payottenland region of Belgium (southwest of Brussels). Similar beers produced outside of this area are usually known as "Lambic-style" or "Plambic" (short for "pseudo-lambic"), although this is purely a voluntary distinction made out of respect to the original.

Unlike conventional ales and lagers, which are fermented by carefully cultivated strains of brewer's yeasts, Lambic beer is instead produced by spontaneous fermentation: it is exposed to the wild yeasts and bacteria that are said to be native to the Senne valley, in which Brussels lies. It is this unusual process which gives the beer its distinctive flavour: dry, vinous, and cidery, with a slightly sour aftertaste.

Types of Lambic

• Lambic (pure): Unblended lambic is a cloudy, uncarbonated, bracingly sour beverage available on tap in only a few locations. Generally three years old. A bottled offering from Cantillon named Grand Cru can be found outside of Belgium.
• Gueuze: A mixture of young (one-year) and old (two and three-year) lambics which has been bottled. It undergoes secondary fermentation (the so-called méthode champenoise), producing carbon dioxide, because the young lambics are not yet fully fermented. It keeps in the bottle; a good gueuze will be given a year to referment in the bottle, but can be kept for 10-20 years.
• Faro: A low-alcohol, slightly sweet table beer made from lambic to which "candi" sugar (crystallised and in some cases caramelised cane or beet sugar) has been added. It is an unblended three-year-old lambic and is usually sold on draught, not bottled.
• Fruit: Lambic with the addition of sour cherry (kriek), raspberry (framboise), peach (pêche), blackcurrant (cassis), grape (druif), or strawberry (aardbei), as either whole fruit or syrup. Other, rarer fruit lambic flavorings include apple (pomme), banana, pineapple, apricot, plum, and lemon. Fruit lambics are usually bottled with secondary fermentation. Although fruit lambics are among the most famous Belgian fruit beers, the use of names such as kriek, framboise or frambozen, cassis, etc. does not necessarily imply that the beer is made from lambic.