A brewery or brewing company is a business that makes and sells beer. The place at which beer is commercially made is either called a brewery or a beerhouse, where distinct sets of brewing equipment are called plant. The commercial brewing of beer has taken place since at least 2500 BC; in ancient Mesopotamia, brewers derived social sanction and divine protection from the goddess Ninkasi. Brewing was initially a cottage industry, with production taking place at home; by the ninth century, monasteries and farms would produce beer on a larger scale, selling the excess; and by the eleventh and twelfth centuries larger, dedicated breweries with eight to ten workers were being built.

Beer is one of the oldest alcoholic drinks in the world, the most widely consumed, and the third most popular drink after water and tea. Beer is produced by the brewing and fermentation of starches from cereal grains—most commonly malted barley, although wheat, maize (corn), rice, and oats are also used. The fermentation of the starch sugars in the wort produces ethanol and carbonation in the beer. Most modern beer is brewed with hops, which add bitterness and other flavours and act as a natural preservative and stabilising agent. Other flavouring agents, such as gruit, herbs, or fruits, may be included or used instead of hops. In commercial brewing, natural carbonation is often replaced with forced carbonation.