The Commonwealth Trans-Antarctic Expedition (CTAE) of 1955–1958 was a Commonwealth-sponsored expedition that successfully completed the first overland crossing of Antarctica, via the South Pole. It was the first expedition to reach the South Pole overland for 46 years, preceded only by Amundsen's expedition and Scott's expedition in 1911 and 1912.

In keeping with the tradition of polar expeditions of the Heroic Age of Antarctic Exploration, the CTAE was a private venture, though it was supported by the governments of the United Kingdom, New Zealand, United States, Australia and South Africa, as well as many corporate and individual donations, under the patronage of Queen Elizabeth II.

It was headed by British explorer Vivian Fuchs, with New Zealander Sir Edmund Hillary leading the New Zealand Ross Sea Support team. The New Zealand party included scientists participating in International Geophysical Year research while the British team were separately based at Halley Bay.

Fuchs was knighted for his accomplishment. The second overland crossing of the continent did not occur until 1981, during the Transglobe Expedition led by Ranulph Fiennes.

Preparations began in London in 1955. Over the austral summer of 1955 to 1956, Fuchs sailed with an advance party from London to Antarctica in the Canadian sealer Theron, with the purpose of establishing Shackleton Base near Vahsel Bay on the Weddell Sea, from which the trans-Antarctic expedition would begin. The Theron, like its immediate forebear, the Endurance, was trapped in the ice. Despite sustaining considerable damage, she was able to free herself with the help of the Auster Antarctic floatplane that scouted a way out. In early 1956, Fuchs sailed back to London, leaving eight men to over-winter at Shackleton.

The eight men of the advance party, led by Ken Blaiklock, were left on the ice, having only tents and a packing crate as shelter. Most of the stores were left on the bay ice, some two miles (3.2 km) from the site of where the base was to be set up. Their first task was to get all these stores from the bay ice to the base and to try to build some permanent shelter for the oncoming winter. Once some food and paraffin had been brought up and the dogs safely tethered by the base, the men started to build their hut. This proved to be far more difficult than had been envisaged – not only were the eight men insufficient in number to carry out the heavy tasks easily but the weather at Shackleton was colder and much windier than had been anticipated.

When the skeleton of the hut was complete, the men positioned the crates containing the wall and roof panels around the building site. Then a blizzard began, and lasted for more than a week. The temperature dropped to −20 °C (−4 °F) and the drift around the base made it impossible to do any work outside. The men sheltered in their crate and slept in their tents which were constantly in danger of getting buried by the drift. When finally the wind subsided the giant crates of wall panels had all disappeared under many feet of drift and the unfinished hut itself was full of snow. The bay ice had broken off taking all the remaining stores with it. Much food and fuel, a couple of huts and a tractor had all gone to sea.

The men tried to retrieve the crates by tunnelling under the snow; the tunnels proved to be useful kennels for the dogs protecting them from the unexpectedly severe winter conditions at Shackleton. The party of eight survived the winter with some difficulty, but in reasonably good health, and finally completed the building of the hut except for one hole in the roof, the panel for which was never found. While the hut was being constructed they lived by day in the tractor crate and slept in their tents, two men to each tent. The winter temperatures often fell well below −30 °C (−22 °F), and Shackleton proved to be a very windy place, which made work outdoors unpleasant. All stores lying in the snow tended to get buried and there was a constant danger of them getting lost.