The flow, flux and routing of water beneath ice sheets has a fundamental impact on their mass-loss behaviour. Relict channelised forms observed on the Antarctic continental shelf imply that there was an active subglacial hydrological system beneath the palaeo Antarctic Ice Sheet. The dimensions of the channelised features is inconsistent with the minimal quantities of meltwater produced under the Antarctic Ice Sheet at present; consequently, their formative mechanism, and its implications for palaeo-ice sheet dynamics, remain unresolved. Here, a compilation of over two decades of multibeam swath bathymetry data, covering a combined area of over 100,000 km2, is used to produce the most comprehensive inventory and quantitatively rigorous analysis of Antarctic submarine channelised landforms to date. Over 2700 bedrock channels are mapped on the inner-continental shelves of the Bellingshausen and Amundsen Seas. Morphometric analysis reveals nearly indistinguishable distributions of channel widths, depths, cross-sectional areas and geometric properties, regardless of geographic location. The channels range in width between 75 m and 3400 m, in depth between 3 m and 280 m, in cross-sectional area between 160 m2 and 290,000 m2 and exhibit V shaped cross sectional geometries that are typically eight times as wide as they are deep. The dimensions and undulating longitudinal profiles of the channels suggest that they are produced by pressurised subglacial meltwater over multiple glacial cycles, potentially in combination with some secondary degree of direct glacial erosion. The channels are comparable, but substantially larger, than the system of channels known as the Labyrinth in the McMurdo Dry Valleys whose genesis has been attributed to catastrophic outburst floods, sourced from subglacial lakes during the Miocene. A similar process origin is proposed for the channels observed on the Antarctic continental shelf, formed through the drainage of relict subglacial lake basins, including some 59 identified through geomorphological evidence and numerical modelling calculations. Water is predicted to accumulate in the subglacial lakes over centuries to millennia and to drain over daily to monthly timescales, potentially having a major impact upon palaeo-ice sheet dynamics.