A microbrewery is a brewery which produces a limited amount of beer.

In the UK, the term has become synonymous with small scale breweries operating under the UK Progressive Beer Duty threshold of 5,000 hls. The most common product is cask conditioned bitter. Breweries are often described by their production capacity or brew length, mostly ranging from 2 to 20 bbls (a brewer's barrel or bbl is 36 imperial gallons (43 US gal; 164 L)).

In the US, the American Brewers Association provides the definition for a "craft brewery" as "small, independent and traditional", and gives a production size of less than 6,000,000 US beer barrels (700,000,000 L) a year (a barrel is 31 US gallons (26 imp gal; 117 L)). A craft brewery can not be more than 24% owned by another alcoholic beverage company that is not itself a craft brewery. The ABA further groups craft breweries as microbrewery: annual production less than 15,000 US beer barrels (1,800,000 L); A "brewpub" brews and sells beer on the premises. A brewpub may also be known as a microbrewery if production has a significant distribution beyond the premises - the American Brewers Association use a fixed 75% of production to determine if a company is a microbrewery.; regional craft brewery: at least 50% of its volume is all malt beers. A regional brewery has annual production between 15,000 US beer barrels (1,800,000 L) and 2,000,000 US beer barrels (230,000,000 L) per year. In order to be classified as a "regional craft brewery" by the brewers association, a brewery must possess "either an all-malt flagship or [have] at least 50% of its volume in either all-malt beers or in beers which use adjuncts to enhance rather than lighten flavor." Of the 1,759 breweries in America, only 43 are not defined as craft brewers, and 100 not defined as either a micro or brewpub.