Stilton is a type of English cheese, known for its characteristic strong smell. It is produced in two varieties: the well-known blue and the lesser-known white. Both have been granted the status of a protected designation of origin by the European Commission, together one of only seventeen British products to have such a designation. Only cheese produced in the three English counties of Derbyshire, Leicestershire, and Nottinghamshire – and made according to a strict code – may be called "Stilton".

It is believed that the pioneer of blue Stilton was Cooper Thornhill, owner of the Bell Inn on the Great North Road, in the village of Stilton. Traditional legend has it that in 1730, Thornhill discovered a distinctive blue cheese while visiting a small farm near Melton Mowbray in rural Leicestershire - possibly in Wymondham, Leicestershire. He fell in love with the cheese and made a business arrangement that granted the Bell Inn exclusive marketing rights to blue Stilton. Soon thereafter, wagon loads of cheese were being delivered to the inn. Since the main stagecoach routes from London to Northern England passed through the village of Stilton he was able to promote the sale of this cheese and the fame of Stilton rapidly spread. The first written reference to Stilton cheese was in William Stukeley’s Itinerarium Curiosum, letter V, dated October 1722.

Frances Pawlett (or Paulet), a skilled cheese maker, of Wymondham, is credited as the person who gave Stilton its first quality and shape standards. Her skill at cheese making and her husband’s business acumen led to the first marketing cooperative in the area for Stilton. Pawlett would come to set the standards other cheese makers would need to meet for “blued cream cheese” good enough to be marketed as Stilton. Along with Thornhill the Pawletts helped build the trade in Stilton cheese to record levels.

In 1936 the Stilton Cheesemakers' Association (SCMA) was formed to lobby for regulation to protect the quality and origin of the cheese, and in 1966 Stilton was granted legal protection via a certification trademark, the only British cheese to have received this status.

Stilton's distinctive blue veins are created by piercing the crust of the cheese with stainless steel needles, allowing air into the core. The manufacturing and ripening process takes approximately nine weeks.

Stilton cheese is made in Derbyshire, Leicestershire and Nottinghamshire. The manufacturers of Stilton cheese in these counties applied for and received Protected Geographical Status (PDO) in 1996 so that production is limited to these three counties and must use pasteurised milk.

There are currently just sixdairies licensed to make Stilton, each being subject to regular audit by an independent inspection agency accredited to European Standard EN 45011. At present, all but one of the licensed dairies are based in the Vale of Belvoir, which straddles the Nottinghamshire-Leicestershire border. This area is commonly regarded as the heartland of Stilton production, with dairies located in the town of Melton Mowbray and the villages of Colston Bassett, Cropwell Bishop (two producers), Long Clawson and Saxelby. The other Leicestershire dairy is at Quenby Hall in Hungarton, which is outside the generally-accepted boundaries of the Vale of Belvoir. Quenby Hall restarted Stilton production in a new dairy in August 2005.

The only licensed dairy that produced Stilton elsewhere (at Hartington in Derbyshire) was acquired by the Long Clawson dairy in 2008 and closed in 2009, with production transferred to Leicestershire.

Oddly, Stilton cheese cannot legally be made in the village that gave the cheese its name. This is because Stilton village is not in the three permitted counties; it is in the administrative county of Cambridgeshire, and in the historic county of Huntingdonshire. There had been no evidence at the time of the application for PDO 1996 that cheese using the same recipe as modern Stilton cheese had ever been made in the village. However recent evidence indicates that it is unlikely that the village would have been a centre for selling of cheese, unless cheese was also made in the area. Furthermore a recipe for a cream cheese made in Stilton in the early 18th century has since been discovered and since more than one type of cheese was usually made, it is possible that a blue cheese was also made in the area.

Stilton has a typical fat content of ~35%, and protein content of ~23%.

A number of blue cheeses are made in a similar way to Stilton. All these cheeses get their blue veins from the saprotrophic fungus Penicillium roqueforti. Examples include Gorgonzola cheese of Italy, which is made from either cows' or goats' milk; and Roquefort, which is made with ewes' milk.

Stichelton is made in the same way as Stilton cheese and uses cows' milk from a permitted county (Nottinghamshire), but the milk is unpasteurised and so under the PDO it cannot be designated as true Stilton.

Since the PDO came into effect, some British supermarkets have been stocking a generic British Blue cheese. Other makers have gained the confidence to adopt their own names, and styles. Blacksticks Blue, Garstang Blue, Cote Hill and Lincoln Blue are typical examples.

Blue Stilton is often eaten with celery or pears. It is also commonly added as a flavouring to vegetable soup, most notably to cream of celery or broccoli. Alternatively it is eaten with various crackers, biscuits and bread. It can also been used to make a blue cheese sauce to be served drizzled over a steak, or can be crumbled over a salad. Traditionally, port is drunk with blue Stilton. The cheese is traditionally eaten at Christmas. The rind of the cheese forms naturally during the aging process, so it is perfectly edible, unlike some other cheeses such as Edam or Port-Salut.

White Stilton has not had the Penicillium roqueforti mould introduced into it which would otherwise lead to the blue veining normally associated with Stilton. It is often blended with other materials such as dried fruit, and has even been used as the flavouring for chocolate.

Huntsman cheese is made with both blue Stilton and Double Gloucester.

A 2005 survey carried out by the British Cheese Board reported that when it came to dream types, Stilton cheese seemed to cause odder dreams than other cheese, with 75% of men and 85% of women experiencing "odd and vivid" dreams after eating a 20-gram serving of the cheese half an hour before going to sleep.

British author G. K. Chesterton wrote a couple of essays on cheese, specifically on the absence of cheese in art. In one of his essays he recalls a time when he, by chance, visited a small town in the fenlands of England, which turned out to be Stilton. His experience in Stilton left a deep impression on him, which he expressed through poetry in his Sonnet to a Stilton Cheese:

Stilton, thou shouldst be living at this hour
And so thou art. Nor losest grace thereby;
England has need of thee, and so have I--
She is a Fen. Far as the eye can scour,
League after grassy league from Lincoln tower
To Stilton in the fields, she is a Fen.
Yet this high cheese, by choice of fenland men,
Like a tall green volcano rose in power.
Plain living and long drinking are no more,
And pure religion reading "Household Words",
And sturdy manhood sitting still all day
Shrink, like this cheese that crumbles to its core;
While my digestion, like the House of Lords,
The heaviest burdens on herself doth lay.

- G.K. Chesterton

This is in part a parody of William Wordsworth's sonnet London, 1802, the opening line of which was "Milton! thou shouldst be living at this hour."

George Orwell wrote an essay, "In Defence of English Cooking", first published in the Evening Standard on 15 December 1945. While enumerating the high points of British cuisine, he touches on Stilton: "Then there are the English cheeses. There are not many of them but I fancy that Stilton is the best cheese of its type in the world, with Wensleydale not far behind."