The bear was revealed by the melting permafrost on the Lyakhovsky Islands in north-eastern Russia.
With its teeth and nose intact, the bear is thought to be a species of brown bear that lived 22,000 to 39,500 years ago.
It will be studied at the North-Eastern Federal University (NEFU) in the city of Yakutsk.
Scientists at the university, known for its research into woolly mammoths and other prehistoric species, suggested the discovery was unprecedented.
Dr Lena Grigorieva, a palaeontology researcher at the university, said the bear was “the first and only find of its kind” to be recovered in once piece with “soft tissue”.
“It is completely preserved, with all internal organs in place, even including its nose,” Dr Grigorieva said.
“Previously, only skulls and bones were found. This find is of great importance for the whole world.”
Dr Grigorieva told the BBC the animal is believed to be an ancient relative of the brown bear, a large species found across Eurasia and North America today.
Other Russian scientists will be invited to join the study, with more details to be announced soon, the NEFU said in a news release on Monday.
“It is necessary to carry out radiocarbon analysis to determine the precise age of the bear,” the university quoted Maxim Cheprasov of the Mammoth Museum laboratory as saying.
The bear carcass was found by reindeer herders on Bolshoy Lyakhovsky Island, the largest of the Lyakhovsky Islands, which are part of the New Siberian Islands archipelago that lies between the Laptev Sea and the East Siberian Sea.
Separately, the preserved carcass of a bear cub was found in Russia’s far-eastern region of Yakutia, also known as the Sakha Republic. DNA testing will be carried out.
Recent years have seen major discoveries of mammoths, woolly rhinos, foal, several puppies and cave-lion cubs as the permafrost melts across vast areas in the Russian region of Siberia.
Last year, an 18,000-year-old puppy was found perfectly preserved with teeth and fur in the permafrost of Siberia.
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