Corey Reid, aged 24, of no fixed abode pleaded guilty to the two offences in a hearing at Oxford Crown Court on Friday (30/10).
Between 5.30pm and 6pm on Saturday 20 April 2019, Reid, who was sleeping rough in Banbury, met and befriended two teenage girls and a teenage boy in the town.
He gave them alcohol and when one of his victims became intoxicated, Reid took her away from the group and sexually assaulted her.
One of the vicitm’s friends called police and Reid was located and arrested.
The victim suffered both psychological and physical injuries as a result of the assault.
Following a thorough investigation, Reid was charged with the offences on 2 June this year and subsequently admitted both offences.
Investigating officer Detective Constable Bryn Smith of the Child Abuse Investigation Unit, based at Banbury police station, said: “Corey Reid is a predatory offender and poses a danger to children.
“His interests are satisfying his own sexual urges towards children, with no thought of consent or their welfare.
“He frustrated the police investigation with silence, and ultimately only pleaded guilty when he realised the evidence against him was so strong that he had no option but to do so.
“The victim in this case has shown incredible bravery throughout this traumatic experience.
“She was vulnerable, not only by her age, but also being intoxicated and targeted deliberately due to this.
“She is still terrified by Reid, who was a complete stranger, and no length of sentence will change that.
“I commend her for her bravery, and I hope that this sentence will act as a stepping stone to a confident and fulfilling future which she fully deserves.
“I would always encourage anyone who has been the victim of a sexual assault to come forward and report it to police.
“You will be listened to and supported by experienced officers and staff, and we will work tirelessly to bring offenders to justice.”