This study aimed to evaluate the water quality of the Tigris River in Baghdad using benthic invertebrate communities as biological indicators A total of 5722 individuals representing 12 taxa were collected including Chironomidae Gammaridae, Thiaridae, Physidae, Lemaneaceae, Nematoda, Tubificidae, Rotifera, Planariidae, and Naididae. Chironomidae was the less abundant group accounting for 27% of the total community followed by Gammarus spp. (25%), while Potamothrix spp. showed the lowest abundance (0.16%). Species richness index (D) values were relatively similar among the studied sites recording 3.25 at S1, 3.30 at S2, 3.16 at S3, and 3.24 at S4 Shannon–Wiener diversity index values ranged from 1.3 to 1.78 with the highest diversity observed at site S3 and the lowest at site S1. The Hilsenhoff Biotic Index (HBI) values ranged from 4.98 to 6.90 indicating low to moderate organic pollution at S1 and moderate to high pollution levels at the other sites The Biological Monitoring Working Party (BMWP) index recorded its highest value at site S1 (21) while the remaining sites showed lower values (15) Correspondingly ASPT values ranged from 2.62 at S1 to 2.14 at the other sites reflecting varying degrees of environmental stress Relative abundance analysis revealed the dominance of three major taxa Chironomidae Gammarus spp. and Melanoides spp. which together constituted more than 60% of the benthic community  Jaccard similarity index showed the highest similarity between sites S1 and S2 (91%) and the lowest between S1 and S4 (75%) cluster analysis supported these patterns highlighting site S1 as the most distinct among the studied locations. Overall the results demonstrate the effectiveness of benthic invertebrates as bio indicators for assessing water quality in the Tigris River and reveal clear spatial variability in environmental conditions associated with different human activities along the river course