The subglacial landscape of Princess Elizabeth Land (PEL) in East Antarctica is poorly known due to a paucity of ice-thickness measurements. This is problematic given its importance for understanding ice-sheet dynamics, and landscape and climate evolution. To address this issue, we describe the topography beneath the ice sheet by assuming ice-surface expressions in satellite imagery relate to large-scale subglacial features. We find evidence that a large, previously undiscovered, subglacial drainage network lies hidden beneath the ice sheet in PEL. We interpret a discrete feature that is 140 × 20 km in plan form, and multiple narrow sinuous features that extend over a distance of ~1100 km. We hypothesize these are tectonically controlled and relate to a large subglacial basin containing a deep-water lake in the interior of PEL linked to a series of long, deep canyons. The presence of 1-km-deep canyons is confirmed at a few localities by radio-echo sounding data, and drainage analysis suggests these canyons will direct subglacial meltwater to the coast between the Vestfold Hills and the West Ice Shelf.