Fears had been growing for Jade Lynch since her various social media profiles had been “silent” following her disappearance from St Helens on 26 March.
The teenager was found in the Wigan area at 9.30pm on Wednesday, said Cheshire Police.
Detective Superintendent Jon Betts said: “I’m pleased to announce that Jade was located safe and well in the Wigan area of Greater Manchester at approximately 9.30pm today.
“Now that we have located Jade we are currently in the process of returning her to a place of safety.
“We will continue to work with our partners to support Jade and her family over the coming days.
“I would like to take this as an opportunity to say a huge thank you to the media and to the public for all of the information and support that you have provided, which has proved vital in our investigation to locate Jade.”
On Tuesday, Jade‘s sister Stephanie Lynch, 22, made an emotional appeal to the teenager.
She said: “All kinds of things are running through our minds. We just want to know that she is safe, that’s all.
“It’s not like her not to be in contact with no-one.”
Earlier on Wednesday, police said they had received a vast amount of information from the public following the appeal with possible sightings of Jade in Manchester city centre.
The schoolgirl, who is originally from the Warrington area, left home at 1pm on March 26 heading for St Helens town centre with her two younger brothers.
While en route, she told her siblings she was going to meet somebody and they parted company in the Duke Street area of the town, where she was last seen.
Police were concerned that Jade appeared to have no access to cash or a mobile phone.