A Scottish trawler found the 3.5m squid in its nets
The 3.15-metre-long (10.3 feet) creature, caught by an Aberdeen-based trawler, will be a star feature at the National Marine Aquarium in Plymouth, Devon.
The squid, believed to be female and three years old, did not survive being brought to the surface.
It is thought it would have stretched to about 5.5m in length if it still had its two feeding tentacles, which were lost when it was caught.
After DNA tests have been conducted, the squid will be preserved in formaldehyde and displayed in its own custom-made tank in the Creatures Of The Deep area of the aquarium's new Ocean Discovery Zone.
The facility will open to the public in May.
"Giant squid are incredibly rare and scientists have never seen one alive," said Doug Herdson, information officer of the National Marine Aquarium.
"They live in very deep waters, at about 500 metres and below, and provide fodder for the sperm whale.
In 1987 a giant squid washed up on the shores of the Shetland Islands.
Others are known from New Zealand and Newfoundland, and a giant squid featured in the Jules Verne novel, 20,000 Leagues Under the Sea.
The aquarium will conduct a number of scientific investigations, in conjunction with experts from the Marine Biological Association and the University of Plymouth, prior to the squid going on display.