The teenager was walking along Black Path in Workington when she was attacked on a grassed area near Cloffocks car park at about 19:30 GMT on Tuesday.
Cumbria Police wants to speak to four boys who were in the area and are believed to have followed the girl along the path.
Officers said the boys are believed to be of a similar age to the victim.
A 15-year-old girl has been raped near a car park in Cumbria.