Ecdysone 20-monooxygenase () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are ecdysone, an electron acceptor AH<sub>2</sub>, and O<sub>2</sub>, whereas its three products are 20-hydroxyecdysone, the reduction product A, and H<sub>2</sub>O.
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O<sub>2</sub> as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derive from O miscellaneous. The systematic name of this enzyme class is . Like other genes in the ecdysone synthesis pathway, it belongs to Cytochrome P450 Halloween genes, with the nickname shade, other names in common use include alpha-ecdysone C-20 hydroxylase, and ecdysone 20-hydroxylase.