New bathymetric, gravity, and magnetic data in the Ross Sea are presented. The bathymetric data show that the entire Ross Sea continental shelf has a mean depth of about 500 metres with the eastern half systematically deeper than the western half. Subdued ridges and valleys characterize the relief of the shelf and trend roughly north-south east of the 18 degrees meridian and northeast-southwest west of it. These features appear to be primarily the result of erosion by past movement of a partially grounded Ross Ice Shelf. The continental slope is tectonically complex especially to the west of Iselin Bank. The most dramatic geophysical feature of the Ross Sea shelf is the linear positive gravity anomaly belt trending north-south across the western Ross Sea. This positive gravity belt is about 700 km long, 50 to 100 km wide, and has an amplitude of up to 80 mgal. We interpret it as marking the position of an ancient rift, probably active during the separation of Australia and New Zealand from Australia. The major sedimentary basin underlying the eastern Ross Sea is not marked by any significant local or regional gravity anomalies and probably contains highly compacted sediments. Large magnetic anomalies over the Ross Sea are few and these are local in extent.