- 74 x 63 km dimension(s)
- Antarctica ()
The record for the largest current iceberg changes hands most years, as new icebergs are calved off the Antarctic continent and subsequently break into smaller fragments. The former record holder was A76, which detached from the Ronne Ice Shelf in the Weddell Sea in May 2021, but which has since fragmented into three pieces. As a result, the new record passes back to A23A, which was measured at 40 x 34 nautical miles (74 x 63 km; 46 x 39 mi), or more than 4,000 square kilometres (1,540 square miles) which is twice the size of Mauritius, on 28 October 2022 as verified by the US National Ice Center.
A23A last held the record in January 2021. Unlike many of the large icebergs that detach from Antarctica and float away, A23A has only moved a few hundred kilometres since it was "born" from the Filchner Ice Shelf in August 1986. This is because it is grounded (stuck) on the seafloor and, as a result, is less vulnerable to fragmenting.
The largest iceberg ever was in excess of 31,000 km2 (12,000 sq mi). It was 335 km long and 97 km wide (208 x 60 mi) – larger than Belgium – and was sighted 240 km (150 mi) west of Scott Island, in the Southern Ocean by the USS Glacier on 12 November 1956. The extent of the iceberg witnessed by the crew of the USS Glacier was estimated, as they did not have the benefit of satellite photography.
The largest iceberg reliably assessed using satellite imagery is iceberg B15, which calved from Antarctica's Ross Ice Shelf in March 2000 and according to NASA measured approximately 300 km long by 40 km wide (186 x 25 mi), with a surface area of 11,000 km2 (4,250 sq mi).