Metathesis (from the Greek μετάθεσις "transposition") may refer to:

  • Metathesis (linguistics), in phonology, a sound change that alters the order of phonemes in a word
    • Quantitative metathesis, a situation in which two vowel sounds follow directly one after the other and a transposition of vowel length takes place
  • Metathesis reaction, in chemistry, a bimolecular process involving the exchange of bonds between the two reacting chemical species
    • Olefin metathesis, an organic reaction which involves redistribution of olefinic (alkene) bonds
    • Alkane metathesis, a chemical reaction in which alkanes are rearranged to give longer or shorter alkane products
    • Alkyne metathesis, an organic reaction involving the redistribution of alkyne chemical bonds