醋，旧称为酰、苦酒等，是烹饪中常用的一种液体酸味调味料。

醋的成分通常含有3%-5%的醋酸，有的还有少量的酒石酸、柠檬酸等。理论上讲，几乎任何含有糖分的液体都可以发酵酿醋。今天，按食醋生产方法，食醋可分为酿造醋和人工合成醋。酿造醋，是以粮食为原料，透过微生物发酵酿造而成。人工合成醋是以食用醋酸，添加水、酸味剂、调味料，香辛料、食用色素勾兑而成。

醋和盐一样在自然环境中可以自行生成，在古巴比伦时代即有醋的记录留下。一般而言，东方国家以谷物酿造醋，西方国家以水果和葡萄酒酿醋。在中国，通常认为醋在西周时开始被酿造，但也有人认为醋起于商朝或更早。汉朝时酰被称为醋。在中东，古埃及时期就已出现了醋。由于都是通过发酵酿造获得，在一定程度上，可以认为酒醋同源，凡是能够酿酒的古文明，一般都具有酿醋的能力。

Vinegar is a liquid consisting of about 5–20% acetic acid (CH₃COOH), water, and other trace chemicals, which may include flavorings. The acetic acid is produced by the fermentation of ethanol by acetic acid bacteria. Vinegar is now mainly used as a cooking ingredient. Historically, as the most easily available mild acid, it had a great variety of industrial, medical, and domestic uses, some of which (such as its use as a general household cleanser) are still promoted today.