The Nobel Peace Prize laureate and anti-apartheid campaigner said that he did "not wish to be kept alive at all costs", writing in the Washington Post newspaper on his 85th birthday.
Mr Tutu came out in favour of assisted dying in 2014, without specifying if he personally wanted to have the choice.
He was hospitalised last month for surgery to treat recurring infections.
"I hope I am treated with compassion and allowed to pass on to the next phase of life`s journey in the manner of my choice," Mr Tutu wrote.
"For those suffering unbearably and coming to the end of their lives, merely knowing that an assisted death is open to them can provide immeasurable comfort."
There is no specific legislation in South Africa governing assisted dying.
But in a landmark ruling in April 2015, a South African court granted a terminally ill man the right to die, prompting calls for a clarification of the laws in cases of assisted death.
Archbishop Desmond Tutu `wants right to assisted death`
07 October 2016
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South Africa`s Archbishop Desmond Tutu has revealed that he wants to have the option of an assisted death.
