Trappist beer is brewed by Trappist breweries. Ten monasteries  - six in Belgium, two in the Netherlands, one in Austria and one in the USA - currently brew and sell Trappist beer.

Trappist beers are all top-fermented and mainly bottle conditioned and may be blonde or brown. Trappist breweries use various systems of nomenclature for the different beers produced which relate to their relative strength, the best known being the system where different beers are called enkel (single), dubbel (double) and tripel (triple). Dubbels are now understood to be a fairly strong (6%-8% abv) brown ale, with understated bitterness, fairly heavy body and a pronounced fruitiness and cereal character. Tripel is used to describe the strongest beer in a brewery's range with an alcohol content ranging from 8% to 10%. Enkels are now no longer brewed as such. Some breweries also use the term blonde for their lightest beers.