Malt is any cereal grain that has been made to germinate by soaking in water and then stopped from germinating further by drying with hot air, a process known as "malting". Malted grain is used to make beer, whisky, malted milk, malt vinegar, confections such as Maltesers and Whoppers, flavored drinks such as Horlicks, Ovaltine, and Milo, and some baked goods, such as malt loaf, bagels, and Rich Tea biscuits. Malted grain that has been ground into a coarse meal is known as "sweet meal".

Malting grain develops the enzymes (α-amylase, β-amylase) required for modifying the grains' starches into various types of sugar, including monosaccharide glucose, disaccharide maltose, trisaccharide maltotriose, and higher sugars called maltodextrines. It also develops other enzymes, such as proteases, that break down the proteins in the grain into forms that can be used by yeast. The point at which the malting process is stopped affects the starch-to-enzyme ratio, and partly converted starch becomes fermentable sugars.

Malt also contains small amounts of other sugars, such as sucrose and fructose, which are not products of starch modification, but which are already in the grain. Further conversion to fermentable sugars is achieved during the mashing process.

Various cereals are malted, though barley is the most common. A high-protein form of malted barley is often a label-listed ingredient in blended flours typically used in the manufacture of yeast bread and other baked goods. The term "malt" refers to several products of the process: the grains to which this process has been applied, for example, malted barley; the sugar, heavy in maltose, derived from such grains, such as the baker's malt used in various breakfast cereals; single malt whisky, often called simply "single malt"; or a product based on malted milk, similar to a malted milkshake (i.e. "malts").

Malted grains have probably been used as an ingredient of beer since ancient times, for example in Egypt (Ancient Egyptian cuisine), Sumer, and China.

In Persian countries, a sweet paste made entirely from germinated wheat is called samanū (Persian: سمنو) in Iran, samanak (Persian: سمنک) in Afghanistan, (Tajik: суманак); (Uzbek Latin: sumalak) or sümölök (Kyrgyz: сүмөлөк), which is prepared for Nowruz (Persian new year celebration) in a large pot (like a kazan). A plate or bowl of samanu is a traditional component of the Haft sin table symbolising affluence. Traditionally, women have a special party to prepare it during the night, and cook it from late in the evening until the daylight, singing related songs. In Tajikistan and Afghanistan, they sing: Samanak dar Jūsh u mā Kafcha zanēm – Dīgarān dar Khwāb u mā Dafcha zanēm (meaning: "Samanak is boiling and we are stirring it, others are asleep and we are playing daf"). In modern times, making samanu can be a family gathering. It originally comes from the Great Persian Empire.^{[citation needed]}

Mämmi, or Easter Porridge, is a traditional Finnish Lenten food. Cooked from rye malt and flour, mämmi has a great resemblance (in the recipe, color, and taste) to samanū. Today, this product is available in shops from February until Easter. A (nonrepresentative) survey in 2013 showed that almost no one cooks mämmi at home in modern-day Finland.

Malting is the process of converting barley or other cereal grains into malt for use in brewing, distilling, or foods, and takes place in a maltings, sometimes called a malthouse, or a malting floor. The cereal is spread out on the malting floor in a layer of 8 to 12 centimetres (3 to 4+1⁄2 inches) depth.