David Goodall, who had been barred from seeking help to end his life in his home country, did not have a terminal illness but said his quality of life had deteriorated significantly and that he wanted to die.
Goodall "died peacefully" in Basel, tweeted Philip Nitschke, founder of Exit International, the organisation which helped Goodall take his own life.
The death occurred at 12:30pm from an infusion of Nembutal, a barbiturate, he said.
At 12.30 today (10th May) Professor David Goodall, 104 years of age, died peacefully at Life Cycle, Basel, Switzerland from an infusion of Nembutal.— Philip Nitschke (@philipnitschke) May 10, 2018
Goodall had on Wednesday burst into song as he told a roomful of journalists that he was looking forward to finally being allowed to end his life.
"I no longer want to continue life," Goodall told the dozens of journalists and television crews who had crammed into a small room at a hotel in the northern Swiss city of Basel to hear him speak, before singing a verse from the Ode to Joy, in German, to loud applause.