The couple were found on the seafront in Ericeira, around 25 north west of Lisbon, on Tuesday (June 12), according coastal authorities in Portugal.
Reports in the Portuguese media said the couple may have fallen 100-feet while taking a picture or trying to recover a mobile phone.
Rui Pereira da Terra, head of the rescue service in the nearby town of Cascais, told Portuguese news agency Lusa officials suspected the man and woman had been taking a selfie when they fell, The Guardian reports.
A Foreign Office spokesperson said: "We are in touch with local authorities following the death of a British woman in Portugal and are providing support to her family."
The woman has been named locally as Louise Benson, the BBC reports.