Abstract: The Yunak Fault Zone is located in the northeast part of the Afyon Akşehir Graben (AAG), which is a seismically active graben in Western Anatolia. During field-based studies, four segments within the Yunak FaultZone were mapped for the first time at a scale of 1/25,000, and named as the Cebrail, Üçkuyu, İncirli, and Ayrıtepe Segments. Their geometric, kinematic, and active tectonic features were analyzed for the first time. The finding sobtained from field studies indicate the presence of faults with lengths ranging from 3 km to 18 km and width sranging from 300 m to 3 km, with orientations varying between NNE-SSW, NE-SW, and E-W, capable of producing earthquakes with magnitudes ranging from 5.6 to 6.7. Paleostress analyses of fault slip data reveal that the NESW trending faults in the region were formed by pure strike-slip faulting under the influence of a N-S directed tensional and E-W directed compressional stress regime during the Miocene-early Pliocene. However, during PlioQuaternary extensional tectonics in western Anatolia, they were reactivated as dip/oblique-slip normal faults within multi-directional extensional tectonics in E-W, NE-SW, and NNE-SSW directions in the north eastern part of theAAG. In this study, the newly identified Akşehir Sub-Graben is controlled by the NE-SW trending dip-slip Yunak and Mevlütlü Fault Zones and exhibits characteristics of a cross-graben on the hanging wall block of the Sultandağı master fault.