Greater Manchester Police said the girl was attacked in Crow Croft Park, Levenshulme, Manchester at about 23:20 BST on Thursday.
Officers were called to the scene following reports of "concern for a teenage girl", said a police spokesman.
He added that police were carrying out inquiries at the scene, which has been cordoned off.
A 12-year-old girl has been raped in a late night attack at a park, police have said.