In molecular biology the 5.8S ribosomal RNA (5.8S rRNA) is a non-coding RNA component of the large subunit of the eukaryotic ribosome and so plays an important role in protein translation. It is transcribed by RNA polymerase I as part of the 45S precursor that also contains 18S and 28S rRNA. Its function is thought to be in 5.8S rRNA ribosome translocation. It is also known to form covalent linkage to the p53 tumour suppressor protein. 5.8S rRNA is also found in archaea.
5.8S rRNA can be used as a reference gene for miRNA detection.