Thames Valley Police are asking for anyone who may have been at Alfred Rose Park on Saturday (13/3) at around 5.45pm.
It's following an incident where a woman aged in her twenties, was walking in Alfred Rose Park with her dog when an unknown man approached her from behind.
The man grabbed the victim around the chest and arms and pulled her close to him before inappropriately touching her over her clothing.
The victim shouted at the offender and then elbowed him in the ribs, causing him to run off towards Dunsham Lane.
The offender is described as a white man, aged approximately 18 years old and about 5ft 8ins tall with an average build. He had a blonde fringe to his hair.
He was wearing a black coat with a hood up, dark tracksuit bottoms, dark shoes and a surgical face mask. He was also carrying a red and black bag.
Police are asking that anybody who was in the vicinity of Alfred Rose Park on Saturday evening who think that they witnessed this incident to please get in touch with them. Or if you recognise the description of the man to also come forward.
Anybody who was in the area and has any information that can assist this investigation should call the 24-hour number 101, quoting reference 43210105656 or make a report online.
Alternatively, for 100% anonymity, you can call the independent charity Crimestoppers on 0800 555 111.