Cytosolic 5'-nucleotidase 3 is an enzyme that in humans is encoded by the NT5C3 gene.

The pyrimidine 5'-nucleotidase (P5N) includes type I and type II isozymes, which catalyze the dephosphorylation of the pyrimidine 5'-monophosphates UMP and CMP to the corresponding nucleosides. This gene encodes the type I P5N isozyme and a gene on chromosome 17 encodes the type II P5N isozyme. Both genes are members of the nucleotidase gene family. Mutations in this gene are the main cause of P5N deficiency, which results in an autosomal recessive hemolytic anemia. It was reported that this gene had two pseudogenes on chromosomes 4 and 7, respectively, but the pseudogene on chromosome 7 is not verified. Alternatively spliced non-coding and coding transcript variants have been found for this gene.
Function: Can act both as nucleotidase and as phosphotransferase.