Ale is a beer style brewed from barley malt with a top-fermenting brewers yeast that ferments quickly, giving a sweet, full body and a fruity, and sometimes a butter-like, taste. Most ale contains some herb or spice, usually hops, which imparts a bitter, herbal flavour which balances the malt sweetness. As an appellative ale means any top-fermented beverage made from malt.

Ales are very common in Britain, Germany, Canada's eastern provinces, Ireland, the United States, and Belgium; however, pale lager is the dominant style of beer in almost all other countries.

An ale is commonly defined by the strain of yeast used and the fermenting temperature.

Ales are normally brewed with top-fermenting yeasts, though a number of British brewers, including Fullers and Weltons, use ale yeast strains that have less pronounced top-fermentation characteristics. The important distinction for ales is that they are fermented at higher temperatures and thus ferment more quickly than lagers.

Ale is typically fermented at temperatures between 15 and 24°C (60 and 75°F). At these temperatures, yeast produces significant amounts of esters and other secondary flavour and aroma products, and the result is often a beer with slightly "fruity" compounds resembling but not limited to apple, pear, pineapple, banana, plum, or prune. Typical ales have a sweeter, fuller body than "lagers".

Differences between some ales and lagers can be difficult to categorise. Steam beer, Kölsch and some modern British Golden Summer Beers use elements of both lager and ale production. Baltic Porter and Bière de Garde may be produced by either lager or ale methods or a combination of both. However, lager production is perceived to produce cleaner tasting, dryer and lighter beer than ale.

Beers classed as ale use predominantly barley malts, though wheat beers and lambics, which also use wheat, are brewed using the ale brewing methods.