At nearly the length of a human arm, the stick insect is not the kind of creepy crawlie you’d want to find sheltering in your bath tub.
Named Phobaeticus Chani - meaning "Chan's megastick" – the insect is more than half a metre with legs outstretched – 55.6cm between the tips of its long spindly legs.
No living examples of the creature have ever been seen, but they are thought to live in the tops of giant rain forest trees on the island of Borneo.
Scientists have only just twigged that the stick insect, which belongs to the Natural History Museum in London, is a new species.
It is more than one centimetre longer than the previous title holder for world’s largest insect.
Dr George Beccaloni, curator of stick insects and their relatives at the Natural History Museum, said: "What seems very likely is that they live at the top of massive rainforest trees, which is why no-one has seen any of them alive. Our specimen probably fell out of a tree or died."
The stick insect, described and named for the first time this week in the journal Zootaxa, was in the hands of a private collector for 10 years before being donated to the museum.
Dr Beccaloni said it was likely the animals were still living undiscovered in the remote forest canopy, but warned they may be in danger.
"The rain forest in Borneo is being badly damaged, and who knows how endangered this species might be,” he said.
"I think it's incredible that it has been left to 2008 to discover the longest insect on the planet. It's amazing that such big things are still out there, and makes you wonder what else there might be."
An unusual feature of P. chani is its eggs. Each egg capsule has wing-like projections on each side, like the flying "snitch" ball in the Harry Potter novels.
The "wings" are thought to allow the eggs to drift in the wind after being laid, helping the species to spread.