Fudge is a confection made by mixing sugar, butter, and milk. Modern fudge has its origins in the 19th century United States, and became popular in American women's colleges late in the century. Fudge can come in a variety of flavorings depending on the region or country it was made; popular flavors include fruit, nut, chocolate, and caramel. Fudge is often bought as a gift from a gift shop in tourist areas and attractions.

In the Oxford Dictionary of Word Origins, the term fudge, used as an expression of annoyance, is traced to the 18th century. This use is described as likely stemming from the earlier "fadge", meaning "to fit".

The creation of fudge in America is typically characterized as accidental, coming about as a cook attempted to make a different confection. Food writer Lee Edwards Benning, drawing on her experimentation with fudge describes the creation as most likely the outcome of "taking the ingredients for caramel and handling them as if making a fondant". Within Britain, various communities in the Midlands and Cornwall had been making local variations of the Scottish sweet, tablet, for centuries which would retroactively be referred to as fudge by the 1890s. Cornish fudge in particular traces its origins to the 18th century, when Cornish confectioners started using clotted cream instead of milk to make their traditional version of tablet.

"Chocolate caramels"—confections made by boiling milk, brown sugar, chocolate, and butter—were popular in the United States during the 1860s and 1870s. These had ingredient ratios and technique close to the modern fudge, and are characterised as a type of fudge by food writer Stella Parks. One of these recipes cited by Parks was published in 1874 in the American agricultural magazine The Cultivator and Country Gentleman, crediting a "Baltimore friend" for "Caramel":

Six ounces of Baker's chocolate; 1 ½ lbs. of brown sugar; ½ lb. butter; 1 cup of milk or cream. Boil 20 minutes; after it begins to boil stirring all the time; pour in pie plates. This quantity makes four plates.

— The Cultivator and Country Gentleman, Vol. 39

Unlike modern fudge, this fudge was stirred consistently, producing a crumbly texture as the syrup crystallized. Another similar recipe appeared in the The Cultivator and Country Gentleman at the end of the decade, again drawing an association with Baltimore. When this confection began to be called fudge is difficult to identify, given the widespread use of 'fudge' in the colloquial sense during the 19th century. By the 1880s and 1890s, mentions of and recipes for fudge appeared widely in American periodicals and advertisements, arriving as prices for sugar and chocolate became increasingly cheap. This early fudge was cut into squares and diamonds and was marketed as a chaste, wholesome treat, contrasting with perceptions of contemporary confections such as luxury bonbons and penny candy. Other than chocolate, early fudge were often flavored with butterscotch, coconut, maple sugar, and vanilla.

The process by which fudge went from crumbly to smooth confection is likewise not firmly known, though Parks posits that the transition can be explained as a consequence of "sheer neglect", as fudge was left to cook over lower temperatures without stirring and the sugar crystals did not crystallize.