Many organic pollutants are ligands of the Aryl hydrocarbon Receptor (AhR), which is a transcriptional factor whose historical function was to regulate the expression of xenobiotic metabolizing enzymes involved in detoxication. Dioxins and aromatic hydrocarbons are ligands and activators of the AhR and lead to various toxicities on animal models. They contaminate the food chain and some of them can also accumulate in adipose tissues (namely the persistent organic pollutants). One critical challenge of toxicology is to define the mechanisms responsible for those toxicities. Recent studies also showed that the AhR regulate numerous genes sometimes without binding to a foreign compound. In this review, we will introduce the AhR and its ligands (exogenous and endogenous compounds) and present the toxicities related to the exposure to such molecules but also its endogenous functions.