Aims: This study was carried out to determine the fish fauna in the Gediz River and by comparing the fish fauna with that of neighboring basins from a zoogeographical point of view. Place and Duration of Study: In order to establish the taxonomic and zoogeographic features of the fish fauna of the Gediz River Basin (Turkey), fish samples were collected using elektrofishing equipment gill nets trammel nets, seine nets and cast nets from June 2010 to July 2012. Methodology: The fish were collected using electrofishing equipment, gill nets (mesh size of 9x9 mm and 12x12 mm), trammel nets (various mesh seize), seine nets (2 mm) and cast nets. The samples were fixed and preserved in a 4% formalin solution. Meristic characters such as number of gill rakers, pharyngeal teeth, dorsal and anal fin rays, total lateral line scales were counted under a stereomicroscope. The last two branched dorsal and anal fin rays are counted “1/2”. The number of vertebrae in the Cyprinidae and Nemacheilidae was determined by radiography. Results: Among the samples, 19 (Anguillidae (1), Cyprinidae (10), Siluridae (1), Nemacheilidae (1), Cobitidae (2), Poeciliidae (1), Gobiidae (1), Percidae (1) and Salmonidae (1)) species belonging to 9 families were identified. Determination of the species; Alburnus battalgilae, Barbus pergamonensis, Luciobarbus lydianus, Capoeta bergamae, Squalius fellowesii, Chondrostoma Original Research Article Guclu and Kucuk; ARRB, 6(3): 202-214, 2015; Article no.ARRB.2015.079 203 holmwoodii, Ladigesocypris mermere, Cobitis kurui, Cobitis fahireae, Oxynoemacheilus simavicus and Knipowtischia mermere are endemic; Gambusia holbrooki and Oncorhynchus mykiss are nonnative species. Conclusion: As a result, in the Gediz River where there were 19 fish taxa, 44% of taxa were endemic. The endemic species on the basis of the IUCN criteria must be especially protected.