The Diplodocus – the life-sized plaster skeleton which has enthralled wide-eyed children for generations – will be moved from his commanding place in the entrance hall in 2017 and replaced by a 25.2m long blue whale skeleton.
Sir Michael Dixon, museum director, said the change is part of a 'decade of transformation' at the central London attraction.
He said: "As the largest-known animal to have ever lived on Earth, the story of the blue whale reminds us of the scale of our responsibility to the planet.
"Species and ecosystems are being destroyed faster than we can describe them or even understand their significance."
Dippy was was bought for the princely sum of £250 in 1891 and originally installed in the Reptile Gallery in 1905.
During the Blitz, he was dismantled and stored in the Natural History Museum's basement for protection.
Although Sir Michael said many people may be upset that 'Dippy' is giving up the limelight, he is hoping to send the dinosaur on tour, so that the diplodocus can be seen by many more people across the country.
He said: "If I am honest there has been concern about Dippy going.
"But a lot of people do not realise that it is not actually a real dinosaur whereas the whale will be the real thing. Which I think is important.
"We're looking to produce another replica that can go outside. Dippy has always been in the middle of a building, and out of context, so this be about putting him in a story of his own time.
"And we are looking into whether it is feasible to do some sort of tour where he will have the opportunity to be seen by a great deal more people, not just people in London."
The blue whale skeleton which is currently on display in the mammals gallery, will welcome visitors into Hintze Hall from summer 2017.
It has been housed at the museum since 1891 after it beached itself at the mouth of Wexford Harbour near the Hantoon Channel, in Ireland, having been injured by a whaler.
It was bought for £250 from Wexford Town merchant William Armstrong. The whale generated 630 gallons of oil that were sold for profit, as well as the remaining meat.It first went on display in 1938 with the opening of the Mammal Hall, where it has been on show, suspended over a 28.6 metre life size model.
Since this whale skeleton came to the Museum in 1891, blue whales have been hunted to near extinction before starting to recover their numbers after they gained protected status.
Sir Michael added: "As the largest known animal to have ever lived on Earth, the story of the blue whale reminds us of the scale of our responsibility to the planet.
"This makes it the perfect choice of specimen to welcome and capture the imagination of our visitors, as well as marking a major transformation of the Museum.
"This is an important and necessary change. As guardians of one of the world's greatest scientific resources, our purpose is to challenge the way people think about the natural world, and that goal has never been more urgent."
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