The victim's body was discovered in woodland at Watlington Hill in Oxfordshire shortly before 6pm on Friday.
Detectives said they were linking the death to reports of a man acting suspiciously near the Fox and Hounds pub in the Christmas Common area of Watlington.
The arrested man was taken to hospital for treatment but remains in custody.
Thames Valley Police said in a statement their Major Crime Unit had launched a murder investigation.
Officers are appealing for help from witnesses who may have seen anything suspicious in the Watlington Hill area in the hours leading up to around 5.50pm.
Detective superintendent Craig Kirby of the Major Crime Unit said on Friday: “We have tonight launched a murder investigation following the discovery of a woman’s body in woodland earlier this evening.
“My thoughts remain with the deceased woman’s family at what must be a hugely distressing time.
“We are carrying out a thorough investigation to piece together what has happened to lead to this woman’s death.
“Officers have located and arrested a man on suspicion of murder, he is currently undergoing hospital treatment for serious injuries.
“We are appealing for the public’s help in our investigation and we are requesting anyone with information to please come forward.
“We are particularly keen on speaking to anyone who may have seen anything suspicious in the Watlington Hill area before or around 5.50pm this evening.
“At this stage we are also tentatively linking this incident to reports of a man acting suspiciously near the Fox and Hounds pub in the Christmas Common area of Watlington at around 3.30pm."
He added: “As such we are also asking anyone who may have seen a man acting suspiciously in this area or anyone who believes they have information that they think could assist us in our investigation to please get in touch."
Anyone with information can call 101 or the Crimestoppers Charity on 0800 555 111.