A friend made the gruesome discovery midday Saurday in the villa where the Swiss couple lived in Saint Cierges, a village of fewer than 500 people in the Gros-de-Vaud district north of Lausanne.
Officers called to scene discovered the lifeless bodies of the 48-year-old woman and her partner in their home, Vaud cantonal police said.
Initial evidence points to a murder-suicide, police said.
The local prosecutor's office is directing an investigation into the case.
The woman, a consulting engineer, and the man, farmer-lumberjack, had been living together for several years and each had children from previous relationships, the ATS news agency reported.
But family members were present when the attacks took place, police said.
“There were no witnesses,” Eric Flaction, cantonal police spokesman told ATS.
Last week, Vaud police reported a 25-year-old man stabbed his 26-year-old girlfriend before finishing her off with a military assault rifle and then turning the gun on himself in their Montreux apartment, east of Lausanne.
The bodies of the Swiss couple were found by a friend on Tuesday, said police, who said a murder-homicide was suspected.
The 20 Minutes newspaper quoted a friend who said the woman was planning to announce she was leaving her boyfriend for good shortly after the pair got together following a brief separation.