Jade Anderson's body was discovered by police at a property in Atherton, near Wigan, at about 14:00 GMT after someone saw the girl unconscious in the house.
Police have not established the cause of death but said her injuries were "consistent with having been attacked by dogs". Four of the dogs were killed.
Jade did not live at the Chaucer Grove home and was thought to be visiting.
Greater Manchester Police said four dogs described as "aggressive and out of control" had since been put down.
Early indications were two of the dogs put down were bull mastiffs and two may be Staffordshire bull terriers, officers said.
Police arrived to find the girl alone in the house and managed to get four of the five dogs contained in the garden.
The force said the animals were then put down "humanely" by armed officers. A fifth dog was securely contained.
The dogs' remains will now be examined as part of the investigation into the incident.
Supt Mark Kenny said: "First and foremost, our thoughts are with the family of the girl who has tragically lost her life.
"I understand this is an extremely distressing incident for all concerned, including the community, and we will work hard to establish the full circumstances that led to this tragedy."
He added there would be a "significant" police presence in the area while police investigated the incident.
Friends have already posted online tributes to Jade on social media websites.
Ellie Morris wrote on Facebook: "Can't believe this has happened. My best friend dead, miss you so much baby girl, my princess. Love you so much, can't believe this has happened.
"You always called me your little sister, told me you will be there for me through thick and thin? Love you baby girl, thinking of you, RIP Jade Anderson, love you."
Another friend, Melissa, who lives across the road, said: "She was amazing, she was actually a really good friend and she was really pretty."
The Department for Environment, Food and Rural Affairs estimates about 210,000 people are attacked by dogs in England every year.
Five children and one adult have been killed by dogs on private property since 2007.
A 14-year-old girl has been found dead at a house where a number of dogs were "out of control".