In molecular biology, snoRNA U73 (also known as SNORD73) is a non-coding RNA (ncRNA) molecule which functions in the biogenesis (modification) of other small nuclear RNAs (snRNAs).

This type of modifying RNA is located in the nucleolus of the eukaryotic cell which is a major site of snRNA biogenesis.

Most of the members of the box C/D family function in directing site-specific 2'-O-methylation of substrate RNAs.

[1] U73 is encoded within the introns of ribosomal protein S3a and contains a 12 nucleotide region of complementarity to a conserved sequence in 28S ribosomal RNA (rRNA).

[2] U73 has been demonstrated to function as a 2'-O-ribose methylation guide RNA for pre-28S rRNA.