Geophysical evidence is presented for an episode of active delamination of a piece of continental lithosphere. Observations of earthquake hypocentre locations, seismic wave velocities and attenuation, Bouguer gravity, seismic reflection and drill hole data are combined with surface geology to infer the presence of a high-velocity, seismically active, rigid body in the upper mantle beneath the Alboran Sea and surrounding Betic and Rif mountain belts of the western Mediterranean region. This upper-mantle body, inferred to be the delaminating continental lithosphere, is overlain by a low-velocity, aseismic and strongly attenuating uppermost mantle, inferred to be the asthenospheric material replacing the delaminating lithosphere.