Antarctica is a major continental mass that has been largely neglected by structural seismologists. In this study, travel-time and short-period amplitude data from natural seismic sources near Antarctica recorded by Antarctic stations are used as constraints to determine a P-wave velocity model for the mantle at depths from ≃100 to 1900 km beneath the Antarctic Shield. Amplitude constraints are included by comparing the observations with synthetic seismograms. The model contains prominent velocity increases near depths of 420 and 650 km, and is similar to those found for some other continental shields. Evidence is found for lateral velocity changes at the ocean-continent and shield-mountain transitions. The direction and magnitude of these changes are consistent with those previously observed for other parts of the Earth.