Feta (Greek: φέτα) is a brined curd cheese traditionally made in Greece. A sheep's milk cheese, varying amounts of goats’ milk may be added, as long as goat milk makes up less than 30% of the total mixture. Since 2005, feta has been a protected designation of origin product in the European Union. Although traditional feta cheese should only include sheep and goat's milk, it is quite common that cheese sold as 'feta' includes cow's milk, or even is composed exclusively of cow's milk.

Feta is an aged cheese, commonly produced in blocks, and has a slightly grainy texture. It is used as a table cheese, as well as in salads, pastries and in baking, notably in the popular phyllo-based dishes spanakopita ("spinach pie") and tyropita ("cheese pie") and combined with olive oil and vegetables.

Similar white brined cheeses (often called 'white cheese' in various languages) are found in the eastern Mediterranean and around the Black Sea.

Feta is salted and cured in a brine solution (based on water or whey) for several months. Feta dries out rapidly when removed from the brine. Feta cheese is white, usually formed into square cakes, and can range from soft to semi-hard, with a tangy, salty flavor that can range from mild to sharp. The cured cheese easily crumbles. Its fat content can range from 30 to 60 percent; most is around 45 percent milk fat. Most feta cheese has a pH of 4.4 to 4.9.

Feta is also an important ingredient of Greek salad. Feta, like most cheeses, can also be served cooked; it is sometimes grilled as part of a sandwich or as a salty alternative to other cheeses in a variety of dishes.

What we nowadays call feta cheese was known to ancient Greeks, at least since Homer's era, as there were several references to it in the Odyssey. The myth has it that the Cyclops Polyphemus was the first cheese manufacturer. Carrying the milk that he collected from his sheep in animal-skin bags, he realised, to his great surprise, that days later the milk had become a solid, savory and preservable mass.

The name Feta (slice) dates back to the 17th century, and it likely refers to the method of cutting the cheese in slices to put it in barrels.

Feta cheese is first recorded in the Byzantine Empire under the name πρόσφατος (prósphatos, "recent", i.e. fresh), and was associated specifically with Crete. An Italian visitor to Candia in 1494 describes its storage in brine clearly.

The Greek word "feta" comes from the Italian word fetta ("slice") It was introduced into the Greek language in the 17th century, likely referring to the method of cutting the cheese in slices to serve on a plate.

Traditionally, feta has been made by peasants in the lower Balkan peninsula from sheep's milk, although goat's milk has been used in more recent times.

After a long legal battle with Denmark, which produced a cheese under the same name using artificially blanched cow's milk, the term "feta" is since July 2002 a protected designation of origin (PDO), which limits the term within the European Union to feta made exclusively of sheep's/goat's milk in Greece. According to the Commission, the biodiversity of the land coupled with the special breeds of sheep and goats used for milk is what gives feta cheese a specific aroma and flavor.

When needed to describe an imitation to feta, names such as "salad cheese" and "Greek-style cheese" are used. The European Commission gave other nations five years to find a new name for their "feta" cheese, or to stop production. Because of the decision by the European Union, Danish dairy company Arla Foods changed the name of their product to apetina.

Similar cheeses can be found in: Albania (djath); Bulgaria (сирене, sirene); Cyprus (χαλίτζι, halitzi);Finland(salaattijuusto, sallad cheese) Republic of Macedonia (бело сирење, belo sirenje, lit. white cheese); Serbia (сир, sir); Israel (gvina bulgarit, lit. Bulgarian cheese); Turkey (beyaz peynir, lit. white cheese); Egypt (domiati); Sudan (gibna beyda); Romania (brânză telemea); Russia (брынза, brynza); Ukraine (бринза, brynza); Iran (panir lighvan); Malta (Ġbejna tan-nagħaġ lit. sheep's cheese) and other countries. In some of these countries, the name "feta" is used interchangeably with the native, while in others "feta" is not used at all or refers to other (mainly imported) types of cheese.