In 1985 many countries joined together to ban whaling because some types were on the verge of extinction, but Japan and Norway still catch them for food. Iceland has now started whaling again after 14 years.
Organisations like the World Wildlife Fund and Born Free, campaign to save animals which are under threat.
Some governments have passed laws to stop certain animals from being hunted.
There are some success stories. The black-footed ferret is extinct in the wild but it's been successfully bred in zoos and is now being released back into the wild.