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 occured at 1030 GMT from an infusion of Nembutal, a barbiturate, he said.
"My feeling is that an old person like myself should have full citizenship rights, including the right of assisted suicide," the 104-year-old added.
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