威末酒（英语：Vermouth，英国发音：/ˈvɜməθ/; 美国发音：/vərˈmuːθ/, ver-MOOTH），也称威末酒或味美思酒（中国大陆），是一种使用各种干料调制的加强葡萄酒。最初于18世纪末和19世纪处在意大利和法国出现。一开始，威末酒作为药用祭酒，直到19世纪后期，它成为了许多经典鸡尾酒的重要成分，比如马丁尼（martini）。

威末酒以葡萄酒为基酒。不同的生产商会在基酒中添加额外的酒精和其他干料混合物，包括香草、植物根茎、树皮，然后装瓶出售。生产的威末酒可分为两个大类，干型的和甜型的。威末酒演化为许多颜色，不过主要还是白色和红色的。除了作为饮料或鸡尾酒配方，有时也会使用威末酒作为烹饪中白酒的替代品。世界各地的大部分威末酒由法国和意大利的公司生产。

Vermouth (/vərˈmuːθ/ ver-MOOTH; also UK /ˈvɜːrməθ/;) is an aromatized wine, a type of fortified wine flavored with various botanicals (roots, barks, flowers, seeds, herbs, spices).

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 19th century it became popular with bartenders as a key ingredient in many classic cocktails that have survived to date, such as the Martini, the Manhattan, the Rob Roy 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.