In the Arabian Platform of SE Turkey abundant evidence exists of fluvial incision by c. 110 ± 10 m since the late Early Pleistocene, starting in or around marine oxygen isotope stage 22 at 870 ka. This incision, which has accompanied regional surface uplift as the isostatic response to regional erosion, has progressively ‘locked’ rivers into their gorges in landscape that formerly had much lower relief. We use this effect to estimate 4.44 ± 0.06 km of left-lateral slip on this time scale on the Gölbaşı–Türkoğlu Fault, a segment of the East Anatolian Fault Zone, from offset river gorges, giving a slip rate of 5.10 ± 0.07 mm a−1. Piercing points indicate that this fault has slipped a total of 19 km, making its age 3.73 ± 0.05 Ma. A total of 33 km of relative motion between the Turkish and Arabian plates is documented on this time scale in the vicinity of Gölbaşı, at an overall time-averaged rate of 8.85 ± 0.12 mm a−1, the estimated Euler vector for relative motion between these plates being 0.89 ± 0.01° Ma−1 about 33.4°N, 42.3°E. This method can be readily applied to determine slip rates, time-averaged since the late Early Pleistocene, on other strike-slip fault zones worldwide.