In enzymology, an adenosine nucleosidase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are adenosine and H<sub>2</sub>O, whereas its two products are D-ribose and adenine.
This enzyme belongs to the family of hydrolases, specifically those glycosylases that hydrolyse N-glycosyl compounds. The systematic name of this enzyme class is adenosine ribohydrolase. Other names in common use include adenosinase, N-ribosyladenine ribohydrolase, adenosine hydrolase, and ANase. This enzyme participates in purine metabolism.