Abstract: The Anatolian Diagonal is a prominent left-lateral shear zone that plays a key role in the neotectonic framework of Türkiye, spanning 170 km between the Central Anatolian and East Anatolian fault zones and extending approximately 850 km from Erzincan to the Cyprus Arc. Its southwestern onshore termination is represented by theEcemiş-Deliler Fault, while its offshore continuation, the Biruni Fault, trends toward the Cyprus Arc. This studyaims to characterise the southwestern end of the Ecemiş-Deliler Fault through geomorphic markers, and to identifythe Biruni Fault using key offshore seismic reflection profiles and geological cross-sections provided by Turkish Petroleum. Focal mechanism solutions for offshore seismic events are also examined to assess fault kinematics.Based on onshore observations, a left-lateral offset of 18 km along the Göksu River indicates a long-term slip rate ofapproximately 2.25 mm/year at the southwestern end of the Ecemiş-Deliler Fault. Offshore, detailed definition andmapping of the Biruni Fault revealed that it comprises a zone of closely spaced, parallel strike-slip segments in itsnortheastern sector, transitioning in a single linear fault trace that extends south westward toward the Aegean Arc. Despite its clear morphological expression, the southwest end of Ecemiş-Deliler fault and the Biruni Fault of theAnatolian Diagonal have low seismic activity, likely because most regional deformation is accommodated furtherwest along the Antalya-Kekova Fault Zone and the Ptolemy–Pliny–Strabo Fault Zone. The restraining stepovers ofthe Antalya Thrust and Fethiye Thrust between these structures provide new insight in a slip partitioning in  the eastern Mediterranean.