In enzymology, a biphenyl synthase () is an enzyme that catalyzes the chemical reaction:
Thus, the two substrates of this enzyme are malonyl-CoA and benzoyl-CoA, whereas its three products are CoA, 3,5-dihydroxybiphenyl, and CO<sub>2</sub>.
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 malonyl-CoA:benzoyl-CoA malonyltransferase. This enzyme is also called BIS.