Sam Woodhead will be taken to Longreach Base Hospital for a medical assessment, Queensland Police said.
The teenager's sister wrote on Facebook: "We have been told that they have found Sam!! We have no information on his condition or where he was found yet, so keep your fingers crossed."
A police spokesman said Sam Woodhead was a little sunburned when he was found, but was hydrated and otherwise well. His family has been notified.
A British backpacker missing in the Australian Outback for more than three days has been found safe and well, Queensland Police said.
A British backpacker who went missing in the Australian outback has been found alive, according Sky News' Australia Correspondent Jonathan Samuels.
A London family are desperately waiting for news after an 18-year-old backpacker went missing in a remote part of Australia. Sam Woodhead from Richmond has not been seen since Tuesday despite a massive search to find him.
Sharon Thomas reports.
A Foreign Office spokesman said:
The sister of a back-packer who has gone missing in Australia has issued an anxious plea for news on Facebook.
Rebecca Woodhead urged people to contact her "ASAP" if they heard anything from her brother Sam.
She wrote: "If anyone hears from my brother please contact me ASAP".
In another posting, she added: "Thanks so much for all your messages regarding Sam.
"Still no further news but we have the helicopter going out again in the morning, Aus time, and hundreds of people going on a voluntary search party. will keep you all posted."
Sam Woodhead, who is 18-years-old and reportedly from Richmond Upon Thames in Surrey, disappeared on Tuesday afternoon after failing to return from a run.
His mother is understood to have urged police to widen the search on the grounds that her son, an experienced long-distance runner, could have travelled some way from his base, near the town of Longreach.
Police have launched a land and air search for a British backpacker missing in the Australian outback after he failed to return after going for a run.
The 18-year-old male, named by local media as Sam Woodhead from London, left the cattle station where he was staying at 5.30pm on Tuesday, but was not found to be missing until Wednesday morning.
Local Sergeant Dave Perry told Brisbane newspaper The Courier-Mail that the owner of the property in the remote town of Longreach, Queensland, had "gone to chase him out of bed" but saw it was empty and call the police.
Described as a "health and fitness fanatic", Queensland Police fear the teenager may have become disorientated while running in unfamiliar territory as temperatures reached 39C in the daytime.
His backpack and running shoes were missing from his room but his other belongings, including his wallet, were still there, police said.