Ribonuclease P (RNase P) is a type of Ribonuclease which cleaves RNA. RNase P is unique from other RNases in that it is a ribozyme-a ribonucleic acid that acts as a catalyst in the same way that a protein based enzyme would. Its function is to cleave off an extra, or precursor, sequence of RNA on tRNA molecules. Further RNase P is one of two known multiple turnover ribozymes in nature (the other being the ribosome), the discovery of which earned Professor Sidney Altman the Nobel Prize in Chemistry in 1989.

In fact, Sidney Altman discovered the existence of precursor tRNA with flanking sequences and was the first to characterize RNase P and its activity in processing of the 5' leader sequence of precursor tRNA back in the 70's.