The incident occurred at around 2.50pm when the victim, who is in her 40s, was approached by a man as she was walking along a footpath in the woods between the vicinity of Esher Road and the Pennyhill Park Hotel.
She was physically attacked by the offender who then carried out the serious sexual assault. The victim screamed for help and the man fled the scene.
The attacker is described as a white man, aged between 16 and 19, approximately 5ft 5inches tall with short, light coloured hair. He was wearing tracksuit bottoms and a white T-shirt and had a bag over his shoulder.
The area where the attack took place has been cordoned off while a forensic team examines the scene and officers are carrying out a number of enquiries in the local area.
Detective Chief Inspector Rachel Bacon, from the Surrey and Sussex Major Crime Team, said: “This was a brazen offence which took place in broad daylight and was a terrifying experience for the victim. She has understandably been left extremely traumatised and is currently being supported by specialist officers.
“I am appealing for anyone who was in the area yesterday afternoon between 2pm and 4pm and may have seen either a man matching the description or any suspicious activity to come forward.
“I would like to reassure the local community that we are doing everything we can to catch whoever was responsible for this crime. This type of incident is thankfully rare but will no doubt cause concern in the local community and we are working closely with residents through the local Safer Neighbourhood Team who will be providing reassurance patrols and visits in the area.
“I would urge anyone who has information which may assist with our investigation to contact Surrey Police immediately. ”
Anyone who can assist detectives with their investigation is asked to contact Surrey Police on 101 quoting reference 45140053383. The independent charity Crimestoppers can be contacted anonymously on 0800 555 111.