A woman was killed by a falling tree branch in Kew Gardens during wet and windy weather conditions on Sunday, police said.
The woman, believed to be about 30, was pronounced dead at the scene.
A Scotland Yard spokesman said officers were called to the Royal Botanic Gardens in south-west London just after 2pm. Paramedics also attended.
The woman's death is not being treated as suspicious and it was not known if the matter would be referred to the Health and Safety Executive (HSE).
"We were called to reports that a large tree branch had fallen on a woman in Kew Gardens," an ambulance service spokesman said.
"We sent an ambulance crew, three responders in cars, an officer and London's air ambulance to the scene.