We report here a slow-moving landslide revealed by Sentinel-1 interferometric time-series analysis. Located along the western coast of the Aral Sea, with a >80-km length and 4-km width, this is the world’s largest active landslide complex reported so far with a constant velocity of 40 mm/yr. Systematic subsidence up to 5 mm/yr, is also observed along narrow strips of terraces that appear to result from rotations of fault-bounded blocks. The horizontal deformation does not correlate with the annual variations of the water level in the Aral Sea over the same period, indicating a long-term forcing of this landslide that might be caused by the long-term sea-level drop. The lateral spreadings involve the competent limestone beds lying horizontally on plastic clay- and evaporite-rich layers. We propose a conceptual model for the mechanism of landslides that appear to be controlled by the attitude of bedding, lithological sequence, hydrogeology, and low angle faults.