The victim, who is in her twenties, was attacked in the early hours of this morning.
She was walking along Church Green just after 1.30am when a man she didn’t know approached her.
He then took her into the churchyard of Saint Mary’s Church, where he raped her.
A scene watch is in place.
Investigating officer, Detective Chief Inspector Lewis Prescott-Mayling said: “We are in the initial stages of our investigation into a rape that was reported to the force in the early hours of this morning.
“A thorough investigation has started in earnest, including a trawl of CCTV in the area, taking statements from numerous witnesses, and forensic examinations at the churchyard of Saint Mary’s Church, where we have instated a scenewatch.
“I would appeal to anyone with any information about the offence to contact Thames Valley Police immediately. The easiest way to contact the force is via our website or by calling 101, quoting investigation reference 43210422024.”