Managers at the zoo say they can no longer afford to keep two-year-old bear, who has lived at the zoo since his birth and become the German city's mascot.
Despite his celebrity status, Berlin Zoo says he must go by 2010 as it will cost at least £7m to pay for bigger enclosures for him and to find him a future mate.
Knut's departure is...bad news for the tourist industry.
It is believed he has raised at least £8.5m in revenue from visits and from the sale of cuddly Knut toys, T-shirts and other merchandise. He is even the subject of a Hollywood film and has graced the cover of Vanity Fair magazine.
But bear experts insist that Knut is re-homed as soon as possible to be with other polar bears.
Zoologists are concerned for his mental welfare and fear that because he only knows contact with humans he has developed psychopathic tendencies....
I can totally relate to developing psychopathic tendencies from too much contact with humans!!!!!
I used to be a sweet boy, too, Knut.
But, come on. Knut ain't a psychopath, is he?
What should we do with Knut?