The newly calved berg, designated A-76 by scientists, was spotted in recent satellite images captured by the Copernicus Sentinel-1 mission, the space agency said in a statement posted on its website with a photo of the enormous, oblong ice sheet.
Its surface area spans 1,668 square miles and measures 106 miles long by 15 miles wide.
By comparison, Spain's tourist island of Majorca in the Mediterranean occupies 1,405 square miles. The U.S. state of Rhode Island is smaller still, with a land mass of just 1,034 square miles.
The enormity of A-76, which broke away from Antarctica's Ronne Ice Shelf, ranks as the largest existing iceberg on the planet, surpassing the now second-place A-23A, about 1,305 square miles in size and also floating in the Weddell Sea.
Some ice shelves along the Antarctic peninsula, farther from the South Pole, have undergone rapid disintegration in recent years, a phenomenon scientists believe may be related to global warming, according to the U.S. National Snow & Ice Data Center.