rRNA N-glycosylase (EC 3.2.2.22, ribosomal ribonucleate N-glycosidase, nigrin b, RNA N-glycosidase, rRNA N-glycosidase, ricin, momorcochin-S, Mirabilis antiviral protein, gelonin, saporins) is an enzyme with systematic name rRNA N-glycohydrolase.

[1] This enzyme catalyses the following chemical reaction Ricin A-chain and related toxins show this activity.

The only protein family known to have this activity is the ribosome-inactivating protein (RIP) family.