The animal has been studied for some time, but new research confirms it is different from all other gibbons, according to BBC.
It has been named the Skywalker hoolock gibbon — partly because the Chinese characters of its scientific name mean ‘Heaven's movement’ but also because the scientists are fans of Star Wars.
The study was published in the American Journal of Primatology.
Dr. Sam Turvey, from the Zoological Society of London, who was part of the team studying the apes, said, "In this area, so many species have declined or gone extinct because of habitat loss, hunting and general human overpopulation.
"So it's an absolute privilege to see something as special and as rare as a gibbon in a canopy in a Chinese rainforest, and especially when it turns out that the gibbons are actually a new species previously unrecognized by science."
Hoolock gibbons are found in Bangladesh, India, China and Myanmar.
They spend most of their time living in the treetops, swinging through the forests with their forelimbs, rarely spending any time on the ground.
But the research team — led by Fan Peng-Fei from Sun Yat-sen University in China — started to suspect that the animals they were studying in China's Yunnan Province were unusual.
All hoolock gibbons have white eyebrows and white beards — but the Chinese primates' markings differed in appearance.
Their songs, which they use to bond with other gibbons and to mark out their territory, also had an unusual ring.
So the team carried out a full physical and genetic comparison with other gibbons, which confirmed that the primates were indeed a different species.
They have been given the scientific name of Hoolock tianxing — but their common name is now the Skywalker hoolock gibbon, thanks to the scientists' taste in films.
Turvey said the team had been studying the animals in the Gaoligongshan nature reserve, but it was not easy.
"It's difficult to get into the reserve. You have to hike up to above 2,500 meters to find the gibbons. That's where the good quality forest usually starts — everywhere below there has been logged.
"Then you have to wake up really early in the morning and you listen out for the haunting song of the gibbons, which carries in the forest canopy.
"And when you hear it, you rush through the mud and the mist, and run for hundreds of meters to try and catch up with these gibbons."
The researchers estimate that there are about 200 of the Skywalker gibbons living in China — and also some living in neighboring Myanmar, although the population size there is currently unknown.
The team warns that the primates are at risk of extinction.
"The low number of surviving animals and the threat they face from habitat loss, habitat fragmentation and hunting means we think they should be classified as an endangered species," said Turvey.