Oreochromis is a large genus in the family Cichlidae (cichlids). It is found in the tribe Tilapiini in the subfamily Pseudocrenilabrinae. Fish belonging to the tribe Tilapiini are commonly referred to as tilapia and you will find many popular food fishes in this tribe. The genus name Oreochromis is derived from the Latin word for gold, aurum.

The genus Oreochromis currently contains over 30 different scientifically described species and there is also a lot of known species that will be placed in the genus once they have been properly described and named.  

The advent of modern technology has caused a lot of commotion in the family Cichlidae and the genus Oreochromis is no exceptions. Modern mitochondrial DNA (mtDNA) sequence analysis has for instance indicated that species such as Oreochromis auerus (Blue tilapia) and Oreochromis urolepis hornorum (Wami tilapia) might be more closely related to the species of the genus Sarotherodon than to the ones in the genus Oreochromis.

Mitochondrial DNA sequence analysis has also revealed that the genus Oreochromis might contain more than one clade. A clade is a taxonomic group consisting of a single common ancestor and all the descendants of that ancestor.

It should be noted that it is hard to use mtDNA sequence analysis for the genus Oreochromis, since the members are known to frequently breed with each other. The resulting hybridization makes mtDNA sequence analysis difficult to interpret. It is also hard to determine which nuclear DNA sequence that is most suitable for sequencing in a genus where evolution works at such great speeds.
Examples of well known fish species belonging to the genus Oreochromis are Mozambique tilapia (Oreochromis mossambicus), Nile tilapia (Oreochromis niloticus), Victoria tilapia (Oreochromis variabilis) and Singida tilapia (Oreochromis esculentus).