Thomas Cooper, formerly of Warmsworth Road, Balby, appeared at Sheffield Crown Court on Friday, February 1, where he was sentenced for a total of 17 years for the assault.
Cooper will serve 12 years in prison, with an extension of five years added due to him being deemed dangerous – the latter will be served in the community.
The 24-year-old pleaded guilty to sexual assault a day before he trial was set to begin.
In April 208, a 14-year-old girl – who cannot be named for legal reasons – was walking through Hexthorpe Park in Doncaster when she became aware of a man, Cooper, approaching her.
Cooper asked the teenager for the time and when she said she was unable to help, he grabbed her and sexually assaulted her.
He then fled the scene, and the victim ran home to report the matter to her parents, who immediately informed police.
Detective Constable Mark Jones said: “Cooper’s victim has been incredibly brave throughout our investigation and was able to work with our officers to provide vital information about her assailant and an e-fit image.
“Following a media appeal to the public, we were contacted by someone who held CCTV footage of a man they thought was behaving suspiciously and closely matched the e-fit. We were able to identify Cooper and arrest him within a few days of the incident occurring.
“I’m grateful for the support of our victim, her family and the wider public as we investigated this concerning crime.
“Cooper is now behind bars for a long time and I hope that the public are reassured by the swift action taken to bring this individual into custody.”