In enzymology, a gibberellin 3beta-dioxygenase () is an enzyme that catalyzes the chemical reaction
The 3 substrates of this enzyme are gibberellin 20, 2-oxoglutarate, and O<sub>2</sub>, whereas its 3 products are gibberellin 1, succinate, and CO<sub>2</sub>.
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as the oxidant. The oxygen incorporated need not be derived from O2 with 2-oxoglutarate as one donor, and one atom of oxygen is incorporated into each donor. The systematic name of this enzyme class is (gibberellin-20), 2-oxoglutarate: oxygen oxidoreductase (3beta-hydroxylating). Other names in common use include gibberellin 3beta-hydroxylase, (gibberrellin-20), 2-oxoglutarate: oxygen oxidoreductase and (3beta-hydroxylating). This enzyme participates in diterpenoid biosynthesis. It has 2 cofactors: iron and Ascorbate.