Knut (German pronunciation: [ˈknuːt] ( listen); 5 December 2006 – 19 March 2011) was a polar bear who was born in captivity at the Berlin Zoological Garden. Rejected by his mother at birth, he was raised by zookeepers. He was the first polar bear cub to survive past infancy at the Berlin Zoo in more than 30 years. At one time the subject of international controversy, he became a tourist attraction and commercial success. After the German tabloid newspaper Bild ran a quote from an animal rights activist that decried keeping the cub in captivity, fans worldwide rallied in support of his being hand-raised by humans. Children protested outside the zoo, and e-mails and letters expressing sympathy for the cub's life were sent from around the world.

Knut became the center of a mass media phenomenon dubbed "Knutmania" that spanned the globe and spawned toys, media specials, DVDs, and books. Because of this, the cub was largely responsible for a significant increase in revenue, estimated at about five million euros, at the Berlin Zoo in 2007. Attendance figures for the year increased by an estimated 30 percent, making it the most profitable year in its 163-year history.

The polar bear (Ursus maritimus) is a bear native largely within the Arctic Circle encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the world's largest land carnivore and also the largest bear, together with the omnivorous Kodiak Bear, which is approximately the same size. A boar (adult male) weighs around 350–680 kg (770–1,500 lb), while a sow (adult female) is about half that size. Although it is closely related to the brown bear, it has evolved to occupy a narrower ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting the seals which make up most of its diet. Although most polar bears are born on land, they spend most of their time at sea. Their scientific name means "maritime bear", and derives from this fact. Polar bears can hunt their preferred food of seals from the edge of sea ice, often living off fat reserves when no sea ice is present.

The polar bear is classified as a vulnerable species, with eight of the nineteen polar bear subpopulations in decline. For decades, large scale hunting raised international concern for the future of the species but populations rebounded after controls and quotas began to take effect.^{[citation needed]} For thousands of years, the polar bear has been a key figure in the material, spiritual, and cultural life of Arctic indigenous peoples, and polar bears remain important in their cultures.