In enzymology, a homoserine O-acetyltransferase (EC 2.3.1.31) is an enzyme that catalyzes the chemical reaction

acetyl-CoA + L-homoserine ${\displaystyle \rightleftharpoons }$ CoA + O-acetyl-L-homoserine

Thus, the two substrates of this enzyme are acetyl-CoA and L-homoserine, whereas its two products are CoA and O-acetyl-L-homoserine.

This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups. The systematic name of this enzyme class is acetyl-CoA:L-homoserine O-acetyltransferase. Other names in common use include homoserine acetyltransferase, homoserine transacetylase, homoserine-O-transacetylase, and L-homoserine O-acetyltransferase. This enzyme participates in methionine metabolism and sulfur metabolism.

As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code 2B61.