In enzymology, a fatty-acid O-methyltransferase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are S-adenosyl methionine and fatty acid, whereas its two products are S-adenosylhomocysteine and fatty acid methyl ester.
This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:fatty-acid O-methyltransferase. Other names in common use include fatty acid methyltransferase, and fatty acid O-methyltransferase.