Fondue is a Swiss and French dish of melted cheese served in a communal pot (caquelon) over a small burner (rechaud), and eaten by dipping long-stemmed forks with bread into the cheese. It was promoted as a Swiss national dish by the Swiss Cheese Union in the 1930's and became popular in North America in the 1960's.

Since the 1950s, the name "fondue" has been generalized to a variety of other dishes where a food is dipped into a hot liquid, including chocolate fondue, where pieces of fruit are dipped into a melted chocolate mixture, and fondue bourguignonne, where pieces of meat are cooked in hot oil.

The earliest known recipe for a dish resembling the modern cheese fondue comes from a 1699 book published in Zurich, under the name "Käss mit Wein zu kochen" 'to cook cheese with wine'. It calls for grated or cut-up cheese to be melted with wine, and for bread to be dipped in it.

The term 'cheese fondue', until the late 19th century, refers to a preparation including eggs and cheese, as in la Chapelle's 1735 Fonduë de Fromage, aux Truffes Fraiches and Brillat-Savarin's 1834 recipe,; it was something between scrambled eggs with cheese and a cheese soufflé. Variations included cream ('à la genevoise') and truffles ('à la piémontaise') in addition to eggs; and also what we now call 'raclette' ('fondue valaisanne').

The first known recipe for the modern cheese fondue under that name, with cheese and wine but no eggs, was published in 1875, and was already presented as a Swiss national dish. Despite its modern associations with rustic mountain life, it was a town-dweller's dish from the lowlands of western, French-speaking, Switzerland: rich cheese like Gruyère was a valuable export item which peasants could not afford to eat.

The introduction of cornstarch ("Maïzena") to Switzerland in 1905 made it easier to make a smooth and stable emulsion of the wine and cheese, and probably contributed to the success of fondue.

Fondue was popularized as a Swiss national dish by the Swiss Cheese Union (Schweizerische Käseunion) in the 1930's as a way of increasing cheese consumption. The Swiss Cheese Union also created pseudo-regional recipes as part of the "spiritual defense of Switzerland". After World War II rationing ended, the Swiss Cheese Union continued its marketing campaign, sending fondue sets to military regiments and event organizers across Switzerland. Fondue is now a symbol of Swiss unity.

The dish became popular in the United States through the late 1960s and early 1970s. In the meantime, fondue continued to be promoted aggressively in Switzerland, with slogans like "La fondue crée la bonne humeur" 'fondue creates a good mood' and (1981) "Fondue isch guet und git e gueti Luune" 'fondue is good and creates a good mood'--abbreviated as "figugegl".

The extension of the name 'fondue' to other dishes served in a communal hot pot dates to 1950's New York. Konrad Egli, a Swiss restaurateur who had popularized cheese fondue, introduced fondue bourguignonne at his Chalet Suisse restaurant in 1956. Then in the mid 1960's, he invented chocolate fondue as part of a promotion for Toblerone chocolate. A sort of chocolate mousse was also sometimes called 'chocolate fondue'.