In enzymology, a pyrimidine-5'-nucleotide nucleosidase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are pyrimidine 5'-nucleotide and H<sub>2</sub>O, whereas its two products are D-ribose 5-phosphate and pyrimidine base.
This enzyme belongs to the family of hydrolases, specifically those glycosylases that hydrolyse N-glycosyl compounds. The systematic name of this enzyme class is pyrimidine-5'-nucleotide phosphoribo(deoxyribo)hydrolase. Other names in common use include pyrimidine nucleotide N-ribosidase, and Pyr5N. This enzyme participates in pyrimidine metabolism.