In enzymology, an inosinate nucleosidase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are 5'-inosinate and H<sub>2</sub>O, whereas its two products are D-ribose 5-phosphate and hypoxanthine.
This enzyme belongs to the family of hydrolases, specifically those glycosylases that hydrolyse N-glycosyl compounds. The systematic name of this enzyme class is 5'-inosinate phosphoribohydrolase. This enzyme participates in purine metabolism.