Gruyère (French pronunciation: [ɡʁy.jɛʁ], English: /ɡruːˈjɛər/ or /ɡrɨˈjɛər/) is a hard yellow cheese made from cow's milk, named after the town of Gruyères in Switzerland, and originated in the cantons of Fribourg, Vaud, Neuchâtel, Jura, and Berne. Before 2001, when Gruyère gained Appellation d'Origine Contrôlée (AOC) status as a Swiss cheese, some controversy existed whether French cheeses of a similar nature could also be labeled Gruyère. (French Gruyère cheeses include Comté and Beaufort.) French Gruyère cheeses must have holes according to French agricultural law, whereas holes are usually not present in Swiss Gruyère.

Gruyère is sweet but slightly salty, with a flavor that varies widely with age. It is often described as creamy and nutty when young, becoming with age more assertive, earthy, and complex. When fully aged (five months to a year) it tends to have small holes and cracks which impart a slightly grainy mouthfeel. To make an 80 kg (176 lb.) round of Gruyère cheese, about 800 litres (211 gallons) of milk are used.

Gruyère is generally known as one of the finest cheeses for baking, having a distinctive but not overpowering taste. In quiche, gruyère adds savoriness without overshadowing the other ingredients. It is a good melting cheese , particularly suited for fondues, along with Vacherin and emmental. It is also traditionally used in French onion soup, as well as in croque monsieur, a classic French toasted ham and cheese sandwich. Gruyere is also used in chicken and veal cordon bleu. It is a fine table cheese, and when grated, it is often used with salads and pastas. It is used, grated, atop le tourin, a type of garlic soup from France which is served on dried bread. White wines, such as riesling, pair well with gruyère. Sparkling apple cider and Bock beer are also beverage affinities.

To make Gruyère, raw milk is heated to 34 °C (93 °F) in a copper vat, and then curdled by the addition of liquid rennet. The curd is cut up into pieces the size of a grain of rice and stirred, releasing whey. The curd is cooked at 43 °C (109 °F), and raised quickly to 54 °C (129 °F). The pieces shrivel up, and the mixture is placed in molds to be pressed. After salting in brine, the cheese is ripened for two months at room temperature, generally on wooden boards. Gruyère can be cured for 3 to 10 months, with long curing producing a cheese of intense flavour.

Gruyère cheeses are very popular in Greece where they are known as γραβιέρα (graviera).

Gruyère cheeses are also produced in the United States, Wisconsin having the largest output.

In 2001 Gruyère gained the Appellation d'origine contrôlée status. Since then the production and the maturation is defined in the Swiss law and all Swiss Gruyère producers must follow these rules. To be accepted throughout Europe as an AOC the “Interprofession du Gruyère” in Switzerland plans to make a transnational AOC with the French producers of Gruyère.

An important and the longest part of the production of the Le Gruyere Switzerland AOC is the "affinage" (French for maturation).

According to the AOC, the cellars to mature a Swiss Gruyère must have a climate close to that of a natural cave. This means the humidity is between 94% to 98%. If the humidity is lower the cheese dries out. If the humidity is too high, the cheese does not mature and becomes smeary and gluey. The temperature of the caves should be between 13 °C (55 °F) and 14 °C (57 °F). This relatively high temperature is only possible if the quality of the cheese is excellent. Otherwise, the temperatures are lower, between 10 °C (50 °F) and 12 °C (54 °F). The lower the temperature is, the less the cheese matures, resulting in a texture that is harder and more crumbly.

Le Gruyère Switzerland AOC has many different varieties, with different aged profiles, and an organic version of the cheese is also sold. There is a special variety that is produced only in summer on the Swiss Alps: the Le Gruyère Switzerland AOC Alpage.

In Switzerland, many other age profiles can be found, including surchoix, vieux, salé, and grotte (cave aged), but these age profiles are not part of the AOC.

Le Gruyère Premier Cru is a special variety, produced and matured exclusively in the canton of Fribourg and matured for 14 months in humid caves with a humidity of 95% and a temperature of 13.5 °C (56.3 °F).

It is the only cheese that has won the title of best cheese of the world at the World Cheese Awards in London three times: in 1992, 2002 and 2005. (The Independent England, 16 March 2005)