In enzymology, a lignostilbene alphabeta-dioxygenase (EC 1.13.11.43) is an enzyme that catalyzes the chemical reaction

1,2-bis(4-hydroxy-3-methoxyphenyl)ethylene + O₂ ${\displaystyle \rightleftharpoons }$ 2 vanillin

Thus, the two substrates of this enzyme are 1,2-bis(4-hydroxy-3-methoxyphenyl)ethylene and O₂, whereas its product is vanillin.

This enzyme belongs to the family of oxidoreductases, specifically those acting on single donors with O₂ as oxidant and incorporation of two atoms of oxygen into the substrate (oxygenases). The oxygen incorporated need not be derived from O₂. The systematic name of this enzyme class is 1,2-bis(4-hydroxy-3-methoxyphenyl)ethylene:oxygen oxidoreductase (alphabeta-bond-cleaving). It employs one cofactor, iron.