An elimination reaction is a reaction in which atoms or groups are removed from two adjacent carbons, creating a new multiple bond between them. It matters as a principal way of making alkenes, for example by removing water from an alcohol or hydrogen halide from an alkyl halide. It is the reverse of an addition reaction and competes with nucleophilic substitution, since the same reagent can often act as either a base or a nucleophile.

消除反应是从两个相邻碳上脱去原子或基团、在它们之间生成一个新的多重键的反应。它之所以重要,是因为它是制备烯烃的主要途径之一,例如从醇脱水或从卤代烷脱去卤化氢。它是加成反应的逆过程,并与亲核取代相互竞争,因为同一种试剂往往既可作碱又可作亲核试剂。