In enzymology, a nucleoside ribosyltransferase (EC 2.4.2.5) is an enzyme that catalyzes the chemical reaction

D-ribosyl-base₁ + base₂ D-ribosyl-base₂ + base₁

Thus, the two substrates of this enzyme are D-ribosyl-base₁ and base₂, whereas its two products are D-ribosyl-base₂ and base₁.

This enzyme belongs to the family of glycosyltransferases, specifically the pentosyltransferases. The systematic name of this enzyme class is nucleoside:purine(pyrimidine) D-ribosyltransferase. This enzyme is also called nucleoside N-ribosyltransferase.

• Koch AL (November 1956). "Some enzymes of nucleoside metabolism of Escherichia coli". The Journal of Biological Chemistry. 223 (1): 535–49. PMID 13376622.