Dehydrohalogenation is an organic reaction in which alkyl halide when boiled with alcoholic alkali gives corresponding alkene. It is also called a β-Elimination reaction and is a type of elimination reaction.

In this reaction, the halogen on the carbon in the alkyl halide reacts with hydrogen present on the β-carbon releasing hydrogen halide. Hence an alkene is formed due to formation of a double bond between the α- and β-carbon. Zaitsev's rule helps to explain regioselectivity for this reaction type. The opposite transformation is called hydrohalogenation.