Mammalian ribosomal proteins are encoded by multigene families that consist of processed pseudogenes and one functional intron-containing gene within their coding regions. Ribosomal Protein S20, also known as RPS20, is a 119 amino acid cytoplasmic protein that is a component of the 40S ribosomal subunit. Co-transcribed with the small nucleolar RNA gene U54, Ribosomal Protein S20 is a primary binding protein (it binds independently to its target protein) that interacts with both the 5’ and 3’ minor domains of 16S ribosomal RNA (rRNA). Through its interactions with 16S rRNA, Ribosomal Protein S20 is thought to play a key role in nucleating the assembly of the 30S ribosomal subunit. Like most ribosomal protein-coding genes, the gene encoding Ribosomal Protein S20 is dispersed throughout the genome and exists as multiple processed pseudogenes.