Experts are yet to examine the whopper, but if original estimates are correct it is about 10 metres long and is 150kg heavier than the next biggest specimen ever found.
The creature is a colossal squid (scientific name Mesonychoteuthis hamiltoni) – a very large species that's shorter but much heavier than the better known giant squid.
The squid was caught after it was hauled to the surface munching on one of its favourite foods – a Patagonian toothfish the fishermen had hooked on a longline.
Dr Steve O'Shea, a world renowned squid expert with the Auckland University of Technology, said the specimen eclipsed the previous largest find – another colossal squid that weighed 300kg found in 2003.
Scientists would be very excited, he said.
"I can assure you that this is going to draw phenomenal interest. It is truly amazing," he said.
He said if calamari were made from the squid the rings would be the size of tractor tyres.
New Zealand Fisheries Minister Jim Anderton described how the squid was hauled from the deep in Antarctic waters.
"It was actually eating a toothfish, which was on a long-line. It was eating it up as it came up," Anderton said.
It is believed the crew on the boat stopped winching in the long-line and spent two hours manoeuvring a net under the squid to haul it aboard.
The squid was caught three weeks ago, but the find was only announced today.
Geoff Dolan, an observer with New Zealand's Ministry of Fisheries, was aboard the vessel San Aspiring, owned by the Sanford seafood company, when the squid was hauled aboard. "There was quite a lot of excitement onboard ... the decision was taken that the chances of survival were not good, and in the interests of science it should be taken on board," Dolan said.Sanford's deepwater division manager Greg Johansson said the squid was barely alive when it was pulled aboard.
"It was deemed that is was more valuable to science," Johansson said.
The squid was taken below deck and stored in a 1200 litre capacity bin, before it was frozen.
It has since been transferred to one of the company's coolrooms in Timaru, on New Zealand's South Island.
It will ultimately end up at the Museum of New Zealand Te Papa Tongarewa in Wellington, where it will be preserved for scientific study.
Colossal squid were first described in 1925 after two tentacles were found in the stomach of a sperm whale.
The creatures live in an area from Antarctica to the southern extremities of South America, South Africa and New Zealand, a statement from the New Zealand Government said.
It said few colossal squid have been sighted, with one was caught in the net of a Russian trawler in the Ross Sea in 1981, another found near the surface in 2003, and another near South Georgia Island in the Southern Atlantic ocean on a toothfish
