Dioxin may refer to a number of different substances. Most notably:

• 1,2-Dioxin or 1,4-dioxin, two unsaturated heterocyclic 6-membered rings in which two carbon atoms have been replaced by oxygen atoms, which gives the molecular formula C4H4O2. 1,2-dioxin is an unstable organic peroxide.

• Dibenzo-1,4-dioxin, also known as dibenzodioxin or dibenzo-p-dioxin (molecular formula C12H8O2), in which two benzene rings are connected through two oxygen atoms. That is the parent compound of the dioxins (see next in which the dioxins comprise a key part of the class).

• Dioxins and dioxin-like compounds, a diverse class of polychlorinated chemical compounds, including polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs), that are persistent organic pollutants and known to exhibit "dioxin-like" toxicity.

• 2,3,7,8-Tetrachlorodibenzodioxin (TCDD), the prototypical and most toxic example of the above class, often referred to simply as "dioxin".

See also

• 1,4-Dioxane, the saturated analog of 1,4-dioxin

• Digoxin

• Dioxin affair, a 1999 crisis in Belgium

• Seveso disaster, a 1976 crisis in Italy