The grisly discovery was made by a member of the public by the Cuxham Road, Willow Close roundabout at Watlington.
They called the RSPCA and inspector Simon Hoggett collected the body on March 2.
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The RSPCA has launched an investigation and the animal welfare charity is appealing for information.
Mr Hoggett said: “The circumstances in which this snake was found are very concerning and it appears this snake has been killed as a result of an act of deliberate cruelty, rather than predation by wildlife.
“The snake’s body had been cut in two pieces and was also decapitated; it appears to have been caused by a blunt cut.
“The snake was a royal python and was around three feet long.
“I am investigating this incident and I would like to hear from anyone that may have information in relation to this incident or may have seen anything suspicious in the area, or who knows who owned a snake matching this description.
“I would urge anyone with information which can help my investigation to call me in confidence on 0300 123 8018.”