Scientists have stuck their necks out and decided that the giraffe is not one species, but four.
Until now, only a single species of giraffe made up of several sub-species had been recognised.
But new DNA evidence shows that four distinct species of the animals exist - and they are genetically at least as different as brown and polar bears.
The unexpected discovery, published in the journal Current Biology, highlights the urgent need to protect the world's tallest mammal, say researchers.
Geneticist Professor Axel Janke, from Goethe University in Germany, said: "We were extremely surprised, because the morphological and coat pattern differences between giraffe are limited."
Giraffes are in dramatic decline across their range in Africa.
In the last three decades their numbers have dropped from more than 150,000 individuals to fewer than 100,000.
Yet relatively little research has been done on giraffes, compared with other large animals such as elephants, rhinoceroses, gorillas and lions, say the researchers.
Professor Janke and his team looked at DNA taken from skin samples from 190 giraffes from across Africa.
Analysis showed there were four highly distinct groups of giraffe, which apparently do not mate with each other in the wild.
The scientists categorised four species of the animal: the southern giraffe (Giraffa giraffa), the Masai giraffe (Giraffa tippelskirchi), the reticulated giraffe (Giraffa reticulata), and the northern giraffe (Giraffa camelopardalis).
The northern giraffe includes the elusive sub-species, the Nubian giraffe, from Ethiopia and South Sudan.
