It's good news for gorillas as experts have discovered two new groups of the really rare animals.
About 125,000 of the great apes were found deep in the forests of the Republic of Congo in central Africa.
It had been thought that there were only about 100,000 of the western lowland gorillas left in total.
The animals can grow up to 1.8m tall and weigh almost 200kg, but they are really shy and hard to find which makes keeping track of them difficult.
The number of gorillas has been going down because of disease, hunting and the destruction of the forest where they live.
Jillian Miller, of the Gorilla Organisation, said the gorillas' discovery was "fantastic news".
She said experts would now work to protect these animals, who are critically endangered.