L-olivosyl-oleandolide 3-O-methyltransferase (, OleY) is an enzyme with systematic name S-adenosyl-L-methionine:L-olivosyl-oleandolide B 3-O-methyltransferase. This enzyme catalyses the following chemical reaction
The enzyme is involved in the biosynthesis of the macrolide antibiotic oleandomycin in Streptomyces antibioticus.