A Thames Valley Police spokesman said: "At just before 8.30pm last night (August 16) officers were called to reports of a body being located in a lake between the A34 and A40 (at Yarnton). Very sadly, the body of a woman was recovered from the water.
"The woman, who has not yet been identified, has shoulder length dark hair and was wearing an olive green waxed jacket and blue jeans.
"Enquiries are ongoing to ascertain the identity of the woman and the death is currently being treated as unexplained."
Detective Inspector Tracey Benham, based at Banbury police station, said: “Tragically, we have located a woman’s body in the water, and we are currently making every effort to identify her and to notify next of kin.
“There will be an increased police presence in the area over the coming days while we make enquiries but I would urge the public not to speculate as to the circumstances.
“We are aware of a woman who was in the area in the last two weeks knocking on doors and I would ask anybody who believes they may have seen a woman matching the description given to please make contact with us either by calling 101 or by making a report online.”
Anybody with any information is urged to call 101 quoting incident reference 2048 (16/8). The online reporting page can be found here.