Butter is a dairy product made from the fat and protein components of churned cream. It is a semi-solid emulsion at room temperature, consisting of approximately 80% butterfat. It is used at room temperature as a spread, melted as a condiment, and used as a fat in baking, sauce-making, pan frying, and other cooking procedures.

Most frequently made from cow's milk, butter can also be manufactured from the milk of other mammals, including sheep, goats, buffalo, and yaks. It is made by churning milk or cream to separate the fat globules from the buttermilk. Salt has been added to butter since antiquity to help preserve it, particularly when being transported; salt may still play a preservation role but is less important today as the entire supply chain is usually refrigerated. In modern times, salt may be added for taste. Food coloring is sometimes added to butter. Rendering butter, removing the water and milk solids, produces clarified butter, or ghee, which is almost entirely butterfat.

Butter is a water-in-oil emulsion resulting from an inversion of the cream, where the milk proteins are the emulsifiers. Butter remains a firm solid when refrigerated but softens to a spreadable consistency at room temperature and melts to a thin liquid consistency at 32 to 35 °C (90 to 95 °F). The density of butter is 911 g/L (15+1⁄4 oz/US pt). It generally has a pale yellow color but varies from deep yellow to nearly white. Its natural, unmodified color is dependent on the source animal's feed and genetics, but the commercial manufacturing process sometimes alters this with food colorings like annatto or carotene.

The word butter derives (via Germanic languages) from the Latin butyrum, which is the latinisation of the Greek βούτυρον (bouturon) and βούτυρος. This may be a compound of βοῦς (bous), "ox, cow" + τυρός (turos), "cheese", that is "cow-cheese". The word turos ("cheese") is attested in Mycenaean Greek. The Latinized form is found in the name butyric acid, a compound found in rancid butter and other dairy products.

Unhomogenized milk and cream contain butterfat in microscopic globules. These globules are surrounded by membranes made of phospholipids (fatty acid emulsifiers) and proteins, which prevent the fat in milk from pooling together into a single mass. Butter is produced by agitating cream, which damages these membranes and allows the milk fats to conjoin, separating from the other parts of the cream. Variations in the production method will create butters with different consistencies, mostly due to the butterfat composition in the finished product. Butter contains fat in three separate forms: free butterfat, butterfat crystals, and undamaged fat globules. In the finished product, different proportions of these forms result in different consistencies within the butter; butters with many crystals are harder than butters dominated by free fats.

Churning produces small butter grains floating in the water-based portion of the cream. This watery liquid is called buttermilk, although the buttermilk most commonly sold today is instead directly fermented skimmed milk. The buttermilk is drained off; sometimes more buttermilk is removed by rinsing the grains with water. Then the grains are "worked": pressed and kneaded together. When prepared manually, this is done using wooden boards called scotch hands. This consolidates the butter into a solid mass and breaks up embedded pockets of buttermilk or water into tiny droplets.

Commercial butter is about 80% butterfat and 15% water; traditionally-made butter may have as little as 65% fat and 30% water. Butterfat is a mixture of triglyceride, a triester derived from glycerol, and three of any of several fatty acid groups. Annatto is sometimes added by U.S. butter manufacturers without declaring it on the label because the U.S. allows butter to have an undisclosed flavorless and natural coloring agent (whereas all other foods in the U.S. must label coloring agents). The preservative lactic acid is sometimes added instead of salt (and as a flavor enhancer), and sometimes additional diacetyl is added to boost the buttery flavor (in the U.S., both ingredients can be listed simply as "natural flavors"). When used together in the NIZO manufacturing method, these two flavorings produce the flavor of cultured butter without actually fully fermenting.

Before modern factory butter making, cream was usually collected from several milkings and was therefore several days old and somewhat fermented by the time it was made into butter. Butter made in this traditional way (from a fermented cream) is known as cultured butter. During fermentation, the cream naturally sours as bacteria convert milk sugars into lactic acid. The fermentation process produces additional aroma compounds, including diacetyl, which makes for a fuller-flavored and more "buttery" tasting product.

Butter made from fresh cream is called sweet cream butter. Production of sweet cream butter first became common in the 19th century, when the development of refrigeration and the mechanical milk separator made sweet cream butter faster and cheaper to produce at scale (sweet cream butter can be made in 6 hours, whereas cultured butter can take up to 72 hours to make).

Cultured butter is preferred throughout continental Europe, while sweet cream butter dominates in the United States and the United Kingdom. Chef Jansen Chan, the director of pastry operations at the International Culinary Center in Manhattan, says, "It's no secret that dairy in France and most of Europe is higher quality than most of the U.S." The combination of butter culturing, the 82% butterfat minimum (as opposed to the 80% minimum in the U.S.), and the fact that French butter is grass-fed, accounts for why French pastry (and French food in general) has a reputation for being richer-tasting and flakier. Cultured butter is sometimes labeled "European-style" butter in the United States, although cultured butter is made and sold by some, especially Amish, dairies.

Milk that is to be made into butter is usually pasteurized during production to kill pathogenic bacteria and other microbes. Butter made from raw milk is very rare and can be dangerous because it is made from unpasteurized milk. Commercial raw milk products are not legal to sell through interstate commerce in the United States and are very rare in Europe. Raw cream butter is generally only found made at home by dairy farmers or by consumers who have purchased raw whole milk directly from them, skimmed the cream themselves, and made butter with it.

Clarified butter has almost all of its water and milk solids removed, leaving almost-pure butterfat. Clarified butter is made by heating butter to its melting point and then allowing it to cool; after settling, the remaining components separate by density. At the top, whey proteins form a skin, which is removed. The resulting butterfat is then poured off from the mixture of water and casein proteins that settle to the bottom.

Ghee is clarified butter that has been heated to around 120 °C (250 °F) after the water evaporated, turning the milk solids brown. This process flavors the ghee, and also produces antioxidants that help protect it from rancidity. Because of this, ghee can be kept for six to eight months under normal conditions.

Cream may be separated (usually by a centrifuge or a sedimentation) from whey instead of milk, as a byproduct of cheese-making. Whey butter may be made from whey cream. Whey cream and butter have a lower fat content and taste more salty, tangy and "cheesy". They are also cheaper to make than "sweet" cream and butter. The fat content of whey is low, so 1,000 pounds of whey will typically give only three pounds of butter.

There are several butters produced in Europe with protected geographical indications; these include:

• Beurre d'Ardenne, from Belgium
• Beurre d'Isigny, from France
• Beurre Charentes-Poitou (Which also includes: Beurre des Charentes and Beurre des Deux-Sèvres under the same classification), from France
• Beurre Rose, from Luxembourg
• Mantequilla de Soria, from Spain
• Mantega de l'Alt Urgell i la Cerdanya, from Spain
• Rucava white butter (Rucavas baltais sviests), from Latvia

Elaine Khosrova traces the invention of butter back to Neolithic-era Africa 8,000 BC in her book. A later Sumerian tablet, dating to approximately 2,500 B.C., describes the butter making process, from the milking of cattle, while contemporary Sumerian tablets identify butter as a ritual offering.

In the Mediterranean climate, unclarified butter spoils quickly, unlike cheese, so it is not a practical method of preserving the nutrients of milk. The ancient Greeks and Romans seemed to use the butter only as unguent and medicine and considered it as a food of the barbarians. A play by the Greek comic poet Anaxandrides refers to Thracians as boutyrophagoi, "butter-eaters". In his Natural History, Pliny the Elder calls butter "the most delicate of food among barbarous nations" and goes on to describe its medicinal properties. Later, the physician Galen also described butter as a medicinal agent only.

In the cooler climates of northern Europe, people could store butter longer before it spoiled. Scandinavia has the oldest tradition in Europe of butter export trade, dating at least to the 12th century. After the fall of Rome and through much of the Middle Ages, butter was a common food across most of Europe—but had a low reputation, and so was consumed principally by peasants. Butter slowly became more accepted by the upper class, notably when the Roman Catholic Church allowed its consumption during Lent from the early 16th century. Bread and butter became common fare among the middle class and the English, in particular, gained a reputation for their liberal use of melted butter as a sauce with meat and vegetables.

In antiquity, butter was used for fuel in lamps, as a substitute for oil. The Butter Tower of Rouen Cathedral was erected in the early 16th century when Archbishop Georges d'Amboise authorized the burning of butter during Lent, instead of oil, which was scarce at the time.

Across northern Europe, butter was sometimes packed into barrels (firkins) and buried in peat bogs, perhaps for years. Such "bog butter" would develop a strong flavor as it aged, but remain edible, in large part because of the cool, airless, antiseptic and acidic environment of a peat bog. Firkins of such buried butter are a common archaeological find in Ireland; the National Museum of Ireland – Archaeology has some containing "a grayish cheese-like substance, partially hardened, not much like butter, and quite free from putrefaction." The practice was most common in Ireland in the 11th–14th centuries; it ended entirely before the 19th century.

Until the 19th century, the vast majority of butter was made by hand, on farms. Butter also provided extra income to farm families. They used wood presses with carved decoration to press butter into pucks or small bricks to sell at nearby markets or general stores. The decoration identified the farm that produced the butter. This practice continued until production was mechanized and butter was produced in less decorative stick form.

Like Ireland, France became well known for its butter, particularly in Normandy and Brittany. Butter consumption in London in the mid-1840s was estimated at 15,357 tons annually.

The first butter factories appeared in the United States in the early 1860s, after the successful introduction of cheese factories a decade earlier. In the late 1870s, the centrifugal cream separator was introduced, marketed most successfully by Swedish engineer Carl Gustaf Patrik de Laval.

In 1920, Otto Hunziker authored The Butter Industry, Prepared for Factory, School and Laboratory, a well-known text in the industry that enjoyed at least three editions (1920, 1927, 1940). As part of the efforts of the American Dairy Science Association, Hunziker and others published articles regarding: causes of tallowiness (an odor defect, distinct from rancidity, a taste defect); mottles (an aesthetic issue related to uneven color); introduced salts; the impact of creamery metals and liquids; and acidity measurement. These and other ADSA publications helped standardize practices internationally.

Butter consumption declined in most western nations during the 20th century, mainly because of the rising popularity of margarine, which is less expensive and, until recent years, was perceived as being healthier. In the United States, margarine consumption overtook butter during the 1950s, and it is still the case today that more margarine than butter is eaten in the U.S. and the EU.

World butter production (cow's milk) and main producing countries in 2018

	Country	Production 2018 (tonnes)
1	United States	892,801
2	New Zealand	502,000
3	Germany	484,047
4	France	352,400
5	Russia	257,883
6	Ireland	237,800
7	Turkey	215,431
8	Iran	183,125
9	Poland	177,260
10	Mexico	153,674
11	United Kingdom	152,000
12	Canada	116,144
13	Belarus	115,199
14	Brazil	109,100
15	Ukraine	100,000
Source : FAOSTAT

In 1997, India produced 1,470,000 metric tons (1,620,000 short tons) of butter, most of which was consumed domestically. Second in production was the United States (522,000 t or 575,000 short tons), followed by France (466,000 t or 514,000 short tons), Germany (442,000 t or 487,000 short tons), and New Zealand (307,000 t or 338,000 short tons). France ranks first in per capita butter consumption with 8 kg per capita per year. In terms of absolute consumption, Germany was second after India, using 578,000 metric tons (637,000 short tons) of butter in 1997, followed by France (528,000 t or 582,000 short tons), Russia (514,000 t or 567,000 short tons), and the United States (505,000 t or 557,000 short tons). New Zealand, Australia, Denmark and Ukraine are among the few nations that export a significant percentage of the butter they produce.

Different varieties are found around the world. Smen is a spiced Moroccan clarified butter, buried in the ground and aged for months or years. A similar product is maltash of the Hunza Valley, where cow and yak butter can be buried for decades, and is used at events such as weddings. Yak butter is a specialty in Tibet; tsampa, barley flour mixed with yak butter, is a staple food. Butter tea is consumed in the Himalayan regions of Tibet, Bhutan, Nepal and India. It consists of tea served with intensely flavored—or "rancid"—yak butter and salt. In African and Asian nations, butter is sometimes traditionally made from sour milk rather than cream. It can take several hours of churning to produce workable butter grains from fermented milk.

Normal butter softens to a spreadable consistency around 15 °C (60 °F), well above refrigerator temperatures. The "butter compartment" found in many refrigerators may be one of the warmer sections inside, but it still leaves butter quite hard. Until recently, many refrigerators sold in New Zealand featured a "butter conditioner", a compartment kept warmer than the rest of the refrigerator—but still cooler than room temperature—with a small heater. Keeping butter tightly wrapped delays rancidity, which is hastened by exposure to light or air, and also helps prevent it from picking up other odors. Wrapped butter has a shelf life of several months at refrigerator temperatures. Butter can also be frozen to extend its storage life.

In the United States, butter has traditionally been made into small, rectangular blocks by means of a pair of wooden butter paddles. It is usually produced in 4-ounce (1⁄4 lb; 110 g) sticks that are individually wrapped in waxed or foiled paper, and sold as a 1 pound (0.45 kg) package of 4 sticks. This practice is believed to have originated in 1907, when Swift and Company began packaging butter in this manner for mass distribution. Due to historical differences in butter printers (machines that cut and package butter), 4-ounce sticks are commonly produced in two different shapes:

• The dominant shape east of the Rocky Mountains is the Elgin, or Eastern-pack shape, named for a dairy in Elgin, Illinois. The sticks measure 4+3⁄4 by 1+1⁄4 by 1+1⁄4 inches (121 mm × 32 mm × 32 mm) and are typically sold stacked two by two in elongated cube-shaped boxes.
• West of the Rocky Mountains, butter printers standardized on a different shape that is now referred to as the Western-pack shape. These butter sticks measure 3+1⁄4 by 1+1⁄2 by 1+1⁄2 inches (83 mm × 38 mm × 38 mm) and are usually sold with four sticks packed side-by-side in a flat, rectangular box.

Most butter dishes are designed for Elgin-style butter sticks.

Outside of the United States, butter is measured for sale by mass (rather than by volume or unit/stick), and is often sold in 250 g (8.8 oz) and 500 g (18 oz) packages.

Since the 1940s, but more commonly the 1960s, butter pats have been individually wrapped and packed in cardboard boxes. Prior to use of cardboard, butter was bulk packed in wood. The earliest discoveries used firkins. From about 1882 wooden boxes were used, as the introduction of refrigeration on ships brought about longer transit times. Butter boxes were generally made with woods whose resin would not taint the butter, such as sycamore, kahikatea, hoop pine, maple, or spruce. They commonly weighed a firkin at 56 pounds (25 kg).

Butter has been considered indispensable in French cuisine since the 17th century. Chefs and cooks have extolled its importance: Fernand Point said "Donnez-moi du beurre, encore du beurre, toujours du beurre!" ('Give me butter, more butter, still more butter!'). Julia Child said, "With enough butter, anything is good."

Melted butter plays an important role in the preparation of sauces, notably in French cuisine. Beurre noisette (hazelnut butter) and Beurre noir (black butter) are sauces of melted butter cooked until the milk solids and sugars have turned golden or dark brown; they are often finished with an addition of vinegar or lemon juice. Hollandaise and béarnaise sauces are emulsions of egg yolk and melted butter. Hollandaise and béarnaise sauces are stabilized with the powerful emulsifiers in the egg yolks, but butter itself contains enough emulsifiers—mostly remnants of the fat globule membranes—to form a stable emulsion on its own.

Beurre blanc (white butter) is made by whisking butter into reduced vinegar or wine, forming an emulsion with the texture of thick cream. Beurre monté (prepared butter) is melted but still emulsified butter; it lends its name to the practice of "mounting" a sauce with butter: whisking cold butter into any water-based sauce at the end of cooking, giving the sauce a thicker body and a glossy shine—as well as a buttery taste.

Butter is used for sautéing and frying, although its milk solids brown and burn above 150 °C (250 °F)—a rather low temperature for most applications. The smoke point of butterfat is around 200 °C (400 °F), so clarified butter or ghee is better suited to frying.

Butter fills several roles in baking, including making possible a range of textures, making chemical leavenings work better, tenderizing proteins, and enhancing the tastes of other ingredients. It is used in a similar manner to other solid fats like lard, suet, or shortening, but has a flavor that may better complement sweet baked goods.

Compound butters are mixtures of butter and other ingredients used to flavor various dishes.

Butter (salted during manufacturing) is 16% water, 81% fat, and 1% protein, with negligible carbohydrates (provided from table source as 100 g). Saturated fat is 51% of total fats in butter (table source).

In a reference amount of 100 g (3.5 oz), butter supplies 717 calories and 76% of the Daily Value (DV) for vitamin A, 15% DV for vitamin E, and 28% DV for sodium, with no other micronutrients in significant content (table). In 100 grams, salted butter contains 215 mg of cholesterol (table source).

Butter, salted

Nutritional value per 100 g
Energy	717 kcal (3,000 kJ)
Carbohydrates	0.06 g
Sugars	0.06 g
Fat	81.1 g
Saturated	51.4 g
Monounsaturated	21 g
Polyunsaturated	3 g
Protein	0.85 g
Vitamins and minerals Vitamins Quantity %DV Vitamin A equiv. 76% 684 μg Vitamin B12 7% 0.17 μg Vitamin E 15% 2.32 mg Vitamin K 6% 7 μg Minerals Quantity %DV Calcium 2% 24 mg Sodium 28% 643 mg
Other constituents	Quantity
Water	16 g
Cholesterol	215 mg
Link to USDA Database entry
Percentages estimated using US recommendations for adults, except for potassium, which is estimated based on expert recommendation from the National Academies.

As butter is essentially just the milk fat, it contains only traces of lactose, so moderate consumption of butter is not a problem for lactose intolerant people. People with milk allergies may still need to avoid butter, which contains enough of the allergy-causing proteins to cause reactions.

Properties of common cooking fats (per 100 g)

Type of fat	Total fat (g)	Saturated fat (g)	Mono­unsaturated fat (g)	Poly­unsaturated fat (g)	Smoke point
Butter	81	51	21	3	150 °C (302 °F)
Canola oil	100	6–7	62–64	24–26	205 °C (401 °F)
Coconut oil	99	83	6	2	177 °C (351 °F)
Corn oil	100	13–14	27–29	52–54	230 °C (446 °F)
Lard	100	39	45	11	190 °C (374 °F)
Peanut oil	100	16	57	20	225 °C (437 °F)
Olive oil	100	13–19	59–74	6–16	190 °C (374 °F)
Rice bran oil	100	25	38	37	250 °C (482 °F)
Soybean oil	100	15	22	57–58	257 °C (495 °F)
Suet	94	52	32	3	200 °C (392 °F)
Ghee	99	62	29	4	204 °C (399 °F)
Sunflower oil	100	10	20	66	225 °C (437 °F)
Sunflower oil (high oleic)	100	12	84	4
Vegetable shortening	100	25	41	28	165 °C (329 °F)

A 2015 study concluded that "hypercholesterolemic people should keep their consumption of butter to a minimum, whereas moderate butter intake may be considered part of the diet in the normocholesterolemic population."

A meta-analysis and systematic review published in 2016 found relatively small or insignificant overall associations of a dose of 14g/day of butter with mortality and cardiovascular disease, and consumption was insignificantly inversely associated with incidence of diabetes. The study states that "findings do not support a need for major emphasis in dietary guidelines on either increasing or decreasing butter consumption."

• List of butter dishes
• List of dairy products
• List of butter sauces
• List of spreads

• Manufacture of butter, The University of Guelph
• "Butter", Food Resource, College of Health and Human Sciences, Oregon State University, 20 February 2007. – FAQ, links, and extensive bibliography of food science articles on butter.
• Cork Butter Museum: the story of Ireland’s most important food export and the world’s largest butter market
• Virtual Museum Exhibit on Milk, Cream & Butter