We measured submarine groundwater discharge (SGD) for the first time in Antarctica, at Lützow-Holm Bay, using a newly developed automated seepage meter. Measured SGD rates ranged from 10−8 to 10−6 m s−1 are substantially greater than previously observed discharge rates at similar depth. The obtained SGD rates are accurate to within 3%–5%. Using a fast Fourier transform, we found that variations in the power spectrum density had a predominant period of 12.8 h, similar to that of the M2 tide, with peak values differing from average SGD rates by a factor of three. The high SGD rates obtained at the Antarctic marginal ice zone may reflect the contribution of significant volumes of subglacial meltwater from the rugged subglacial mountains located about 20 km inland from the coast. We discuss a possible mechanism of meltwater discharge to this coastal region.