Vermouth is an aromatized fortified wine flavored with various botanicals (roots, barks, flowers, seeds, herbs, spices). It is said to be the most versatile of all cocktail ingredients. The modern versions of the beverage were first produced in the mid to late 18th century in Turin, Italy. While vermouth was traditionally used for medicinal purposes, its true claim to fame is as an aperitif, with fashionable cafes in Turin serving it to guests around the clock.

However, in the late 1800s it became popular with bartenders as a key ingredient in many classic cocktails that have survived to date, such as the Martini, the Manhattan and the Negroni. In addition to being consumed as an aperitif or cocktail ingredient, vermouth is sometimes used as an alternative white wine in cooking.

Historically, there have been two main types of vermouth, sweet and dry. Resulting from demand and competition, vermouth manufacturers (e.g., Noilly Prat and Cinzano) have created additional styles, including extra-dry white, sweet white (bianco), red, amber (ambre or rosso), and rosé. Vermouth is produced by starting with a base of a neutral grape wine. Each manufacturer adds additional alcohol and a proprietary mixture of dry ingredients, consisting of aromatic herbs, roots, and barks, to the base wine.

After the wine is aromatized and fortified, the vermouth is sweetened with either cane sugar or caramelised sugar, depending on the style. Italian and French companies produce most of the vermouth consumed throughout the world.