The relationship between landslides and rock mass strength is fundamental for assessing landslide hazards. Some researchers have proposed that there is an inverse relationship between the number of landslides and rock mass strength. However, in some tectonically active mountain ranges, higher rates of landsliding appear to be associated with greater rock mass strength. We investigated the relation between landslides and rock mass strength in the Langxian (LX), Lulang (LL), and Tongmai (TM) regions in southeastern Tibet by identifying and mapping 294 large bedrock landslides using 10-m resolution lidar bare-earth imagery. An inverse relationship between topographic relief and the slope angle of historical landslides demonstrates that rock mass strength is an important factor controlling relief in the study area. Applying Culmann's method, we back-calculated rock mass strengths ranging from 60 to 770 kPa at the landscape scale. Our data show that, at the landscape scale, more landslides have occurred on the hillslopes with greater rock mass strength than on those with lower rock mass strength. We conclude that the stability of slopes in our study areas is controlled by rock mass strength, but the dominant drivers of failure are rock uplift and river incision, rather than a reduction in rock strength as has been proposed in some tectonically passive regions.