The attack took place near the Sands Hotel in Lochies Road, Burntisland, between 20:30 and 22:00 on 25 June, but was not reported to police until Tuesday.
Police said no description of the suspects was available.
Officers want to speak to anyone who remembers seeing anything suspicious in the area at the time of the incident.
They would also like to hear from anyone who remembers seeing the victim, who is described as slim with long blonde and pink hair. She was wearing black leggings, a black crop top and a light-coloured jacket.
Det Insp June Peebles said: "We are currently trying to determine exactly what has happened during this incident and would urge members of the public who can assist with our investigation to come forward."
Police have appealed for witnesses after a 15-year-old girl was sexually assaulted by two men in Fife.