Ten glacial megaclasts, unique perhaps from a global perspective, have been identified in the half-graben rift of the MacDonald Corridor. The MacDonald Corridor is the most easterly of four half-grabens containing Neoproterozoic low-grade metasedimentary rocks situated between inliers of Palaeoproterozoic-Mesoproterozoic basement at the south-western margin of the Curnamona Province. These corridors originated as extensional structures during the last of three major episodes of rifting that led to the eventual break-up of the supercontinent Rodinia. This rift phase was synchronous with the older (Sturtian-age) of the two major Cryogenian glaciations of the 850–600 Ma glacio-epoch that are recorded in the rift complex of the Adelaide Geosyncline in South Australia. It was during this epoch that complex life forms, including the first animals, evolved on Earth. Sedimentation in the MacDonald Corridor half-graben commenced in the early Sturtian, with deposition of siltstone and quartzite of the Belair Subgroup of the Burra Group. These are disconformably overlain by the glacially-related Yudnamutana Subgroup, comprising diamictite and sandstone of the Pualco Tillite, succeeded by the conformably overlying Benda Siltstone, followed unconformably by the Wilyerpa Formation. The Benda Siltstone contains abundant dropstones demonstrating the presence of floating ice, and interfingers on all scales with a complex variety of facies, including cross-bedded and structureless sandstones, the bedded sedimentary Braemar ironstone facies, diamictite (both ferruginous and non-ferruginous), arkosic grit, and the Old Boolcoomata Conglomerate Member composed predominantly of clasts of Bimbowrie Suite granite. Mostly the conglomerate occurs only in the lower part of the Benda Siltstone, but it interfingers to such an extent that it locally makes up the whole thickness of this unit. This latter feature, the Christmas-tree Fan, is an accumulation of coarse debris derived from a granitic source within the adjacent Kalabity (basement) Inlier. The megaclasts have been mapped within the sedimentary fill of the MacDonald Corridor half-graben. The largest, MC 1, is a granite slab at least 1.25 km in width that was emplaced from the south-east, perhaps sourced from the Binberrie Hill granite. The hosting sandstone beds of the Pualco Tillite were severely disrupted by emplacement, which was localised into a pre-existing structural depression in the sandstone. Bedded ironstone laps onto the upper surface of the granite slab, which snapped in half when it came to rest. MC 2 is a much smaller granite megaclast nearby. MC 3 is a 450 m wide megaclast of albitic and migmatitic metasediment intruded by granite which has the appearance of a very large dropstone in bedded ironstone; its source was not the immediately adjacent basement, but must have been at least several kilometres away. MC 4 is also metasedimentary, situated within an upper tongue of conglomerate. MC 5 is a series of tabular granite bodies embedded in another conglomerate tongue. MC 6 is a metasedimentary megaclast that has moved little from its source and is incorporated into the fill of a U-shaped glacial valley carved into the Binberrie Hill granite. MC 7, 8 and 9 are granitic megaclasts situated near the western edge of the Kalabity Inlier, while MC 10 has limited outcrop and is largely inferred from its signature on radiometric imagery as a large metagranite-derived body. The megaclasts are compared with olistoliths, rock slides and glacial erratics, but no direct analogs have been found, so that it is possible that megaclast MC 1 is the largest of its type known in the world. Tectonic activity was responsible for creating high-relief topography on the Kalabity Inlier, and ice action carved a U-shaped valley into the resulting granite mountains. Ice was also instrumental in separating the megaclasts from their source and transporting them into the tectonically active MacDonald Corridor half-graben.