His exploits beat yawning hippos, headless penguins and apparently flying horses to take the Creatures of the Land category and the overall title.
Photographer Jennifer Hadley explained the events behind the shot. “He wanted to get down and walked all over the branches looking for the right spot and finally just went for it,” she said.
“It was probably his first time in a tree and his descent didn't go so well. He was just fine, though, after landing on the ground. He got up and ran off with some other cubs.”
The Affinity Photo 2 People’s Choice Award, voted for by the public, also went to Ms Hadley for her charming shot of two stroppy penguins entitled Talk to the Fin!
Arturo Telle Thiemann won the underwater category with his shot of grey trigger fish in the Azores smiling for the camera.
Jia Chen was awarded the Amazing Internet Portfolio Award for Football Dream — four images of a Cooper's hawk playing football.
The winner of the Think Tank Photo Junior Category was Arshdeep Singh, who entered a shot of a winking owl resting in a pipe.
Ms Hadley was up against 5,000 entries from more than 85 countries and her image fought off fierce competition in what organisers said was its closest vote to date.
The photo, captured in the Serengeti, Tanzania, captured the moment the three-month-old cub tried to climb down a tree.
Ms Hadley wins a trip to the Masai Mara, Kenya, with Alex Walker’s Serian safari company.
“I think part of what makes this contest great is that most of these photos probably happen by complete accident and that was certainly the case with the lion cub falling out of the tree,” she said.
“It didn't even occur to me that he would make a go of getting down by himself in the most un-cat like fashion. I mean, how often do cats fall out of trees?
“The gasp that emanated from our vehicle was palatable," she added. "No one expected this to happen and of course we were concerned for his safety, but happily, as cats do, he righted himself just in time and landed on all fours and ran off with his siblings. A happy ending for a hapless kitty who didn't quite know how to get down from a tree.”
The awards were founded in 2015 by Paul Joynson-Hicks and Tom Sullam, both professional photographers and passionate conservationists.
This year’s charity beneficiary is the Whitley Fund for Nature, which supports conservation leaders working in their home countries across the Southern Hemisphere.