In order to study the biostratigraphy of the Gurpi Formation in the Fars area, a stratigraphic section is selected and sampled in the Sarbalesh anticline. The thickness of the Gurpi Formation in this section is 346.3 meters and its main lithology includes argillaceous limestone and shale. The lower boundary with the Sarvak Formation indicates a disconformity with dissolution holes and iron oxide bearing fragments, and its upper boundary with the Pabdeh Formation indicates a disconformity with a 30 cm thick key horizon containing phosphate nodules and manganese oxide traces. In this study, by identifying 66 species belonging to 22 genera of planktonic foraminifera, 9 biozones were identified and introduced based on the Tethys standard biozonation of Permoli Silva and Verga (2004). The age of the Gurpi Formation based on identified biozones is determined from the early Santonian to the late Maastrichtian. The K/Pg boundary is located at the end of the key horizon containing phosphate nodules and correlates with the lithostratigraphic boundary of the Gurpi and Pabdeh formations.