Goodall, who pushed for legalization of assisted dying in Australia, received more than $20,000 in donations from the public to fund his trip to the clinic in Switzerland. "I am content to leave them undone".
Tom Curran, a Director of Exit International, was with David up until the end along with family and other supporters.
"I am happy to have this opportunity, which I call the Swiss option", he said after arriving this week.
Several US states have a form of physician-assisted suicide, as do a small number of countries including Japan, Belgium and Switzerland.
Critics have said that Goodall's death was not simply a personal choice, but a political one that could have devastating consequences on vulnerable populations such as the elderly, the poor, and the disabled.
Goodall meets all the requirements for seeking an assisted death, despite the fact that he is not terminally ill.
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Philip Nitschke, founder of the foundation that helped him take his life, revealed that he did not have a terminal illness but wanted to end his life because his quality of life had deteriorated. Starting in June 2019, terminally ill patients who have a life expectancy of less than six months can request a lethal drug to end their lives. He wished to have no funeral, remembrance service or ceremony, since he had "no belief in the afterlife".
His supporters applauded his decision to take charge of his fate after declaring his life was no longer worth living.
He said he would have preferred to die in Australia and previously voiced his resentment over the country's laws.
Afterward, Goodall said he was considered incapable of looking after himself.
Professor Goodall continued his scientific research, commuting daily to his office at Edith Cowan University, until the age of 103.
"I no longer want to continue life", he said. Then I have a bit of lunch and just sit.
Earlier this week, Goodall said he resented having to travel so far to carry out his plan, but was relieved the end was near. "It's my own choice to end my life tomorrow and I look forward to that and I'm grateful to the Swiss nation to make that possible", he added, expressing optimism his story will help forward the cause he was so passionate about.
Dr Goodall will likely become the 45th person from Australia to have undergone euthanasia in a foreign country.