Berkner Island or Berkner Ice Rise or Hubley Island is a high and completely ice-covered large island about 320 km (200 miles) long and 135 km (85 miles) wide in Antarctica, with an area of 43873.1 km² (16939.42 mi²). It is the second largest island of both Antarctica and the British Antarctic Territory, after Alexander Island. It is also located within the Argentine Antarctic claim. Berkner Island is the southernmost island of the world, a title that is sometimes incorrectly awarded to Ross Island. Berkner Island is however - other than Ross Island - not accessible from the sea, since it is completely surrounded by ice shelf. The northernmost point of the island is still about 17 km from the open sea.
The island rises to 869 m (975 m or 3,200 ft according to other sources) and separates Ronne Ice Shelf from the Filchner Ice Shelf. It is characterized by two domes, Reinwarthhöhe in the north (698 m), at , and Thyssenhöhe in the south (869 m), at . It is indented by three bays on the eastern side, which are from north to south: McCarthy Inlet, Roberts Inlet, and Spilhouse Inlet. Gould Bay is on the north coast. Berkner Island is about 150 km west of Luitpold Coast, Coats Land, the closest mainland of Eastern Antarctica. 17 km off the northwest corner of Berkner Island is Hemmen Ice Rise.
Berkner Island was discovered by members of the United States-International Geophysical Year (US-IGY) party at Ellsworth Station under the leadership of Capt. Finn Ronne, United States Navy Reserve (USNR), during the 1957-1958 season. Berkner Island was named by the United States Advisory Committee on Antarctic Names (US-ACAN) for American physicist Lloyd Berkner, engineer with the Byrd Antarctic Expedition (1928-1930).
Since 1990, Berkner Island has been a jumping off point for a number of long distance polar expeditions. In 2009 SOUTH.com, the first unsupported return journey to the South Pole, will begin from there.
In the 1994/1995 field season the British Antarctic Survey, Alfred Wegener Institute and the Forschungsstelle für Physikalische Glaziologie of the University of Münster cooperated in a project drilling ice cores on the North and South Domes of Berkner Island.