The body was also missing an arm and both feet, Il Messaggero reported.
The grim discovery was made by a passer-by walking their dog along Scivu beach, on the island’s Costa Verde, on Wednesday evening.
Police believe the woman could have fallen overboard from a foreign ship or be a migrant who drowned while making the treacherous crossing from north Africa.
They estimate the body could have been in the water for “two to four months”. The body is likely have been attacked by fish and “corroded” by the sea, Il Messaggero reported.
Police at this stage have ruled out murder, as an autopsy showed there were no signs of violence on the body.
The autopsy also showed that the woman was 1.65 metres tall and could be described as either Caucasian or African due to the skin colour. The woman had also been wearing a pair of size 46 trousers.
Police are now checking cases of missing people in Sardinia and have made contact with French and Italian police forces for any feedback on accidents at sea.