Demethylspheroidene O-methyltransferase (, 1-hydroxycarotenoid O-methylase, 1-hydroxycarotenoid methylase, 1-HO-carotenoid methylase, CrtF) is an enzyme with systematic name S-adenosyl-L-methionine:demethylspheroidene O-methyltransferase. This enzyme catalyses the following chemical reaction
In Rhodopseudomonas capsulata and Rubrivivax gelatinosus the enzyme is involved in biosynthesis of spheroidene.