"Dioxins" refers to a group of chlorinated organic chemicals with similar chemical structures.

Dioxins have no uses. They are formed unintentionally and released as byproducts of waste incineration and other human activities such as fuel combustion, chlorine bleaching of pulp and paper, or pesticide manufacturing. They are also formed by natural processes such as forest fires and volcanoes.

Some dioxins have harmful properties, depending on the number and position of chlorine atoms. One of the most toxic dioxin is known as TCDD (2,3,7,8 tetrachlorodibenzo-p-dioxin).