This study focused on identifying Keratella quadrata (K. quadrata) collected from Shatt Al-Basrah, South of Iraq. After sampling and isolation, the extracted DNA from isolates of K. quadrata was subjected to PCR technique to amplify the 18S rRNA gene which amplified 1759 bp fragment. Those sequences with a similarity rate of ≥99% of K. quadrata were considered as the common species. The phylogenetic tree unraveled the distribution and phylogenetic relationships among the studied Keratella species and their identical reference strains according to CLUSTAL W program. The extracted DNA from Keratella isolates identified one K. quadrata species, which was different from those in previous studies in Basrah province and Iraq and the global isolates of K. quadrata sequence registered in the NCBI of USA, ENA of Europe and DDBJ of Japan. with KX358062.1 accession number. It was concluded that more large sampling studies are required to identify and classify the taxonomy of Rotifera species.