吸烟（英语：Tobacco smoking，或称抽烟，粤语与闽语皆作食烟）是从燃烧烟草产品吸入其烟及化学成份，特别是吸香烟、吸雪茄、吸烟斗等行为，香烟的主要成份包括尼古丁、焦油及一氧化碳。吸烟行为其实同时损害吸烟者及附近被动地吸二手烟者的健康，因此欧盟及美国都允许雇主拒绝聘用及开除吸烟者，而许多国家也规定室内公共场所不得吸烟、禁烟令也开始延伸至许多室外场所、甚至有一些地方甚至立法禁止私人住宅吸烟。吸烟者及被动吸烟者也会吸入数千种有害化学物质，吸烟除了引致口气、牙渍、咳嗽、痰多或喉部不适，更会引致各种病症。

Tobacco smoking is the practice of burning tobacco and inhaling the smoke (consisting of particle and gaseous phases). (A more broad definition may include simply taking tobacco smoke into the mouth, and then releasing it, as is done by some with tobacco pipes and cigars.) The practice was believed to begin as early as 5000–3000 BC . Tobacco was introduced to Eurasia in the late 17th century where it followed common trade routes. The practice encountered criticism from its first import into the Western world onwards, but embedded itself in certain strata of a number of societies before becoming widespread upon the introduction of automated cigarette-rolling apparatus.