40S ribosomal protein S25 (eS25) is a protein that in humans is encoded by the RPS25 gene. Ribosomes are cellular macromolecules that catalyze protein synthesis across all kingdoms of life. The eukaryotic ribosome consists of a small 40S subunit and a large 60S subunit. Together these subunits are composed of 4 RNA species and approximately 80 distinct proteins. The RPS25 gene encodes the eukaryote-specific ribosomal protein eS25 that is a component of the 40S subunit. As is typical for genes encoding ribosomal proteins, there are multiple processed pseudogenes of this gene dispersed through the genome.