cruise ship in Cape Town, celebrating a career that earned a Nobel Peace Prize for battling apartheid and gave voice to South Africa`s conscience.
Tutu announced in July that he would step down from public life on his 79th birthday, which he will ring in Thursday with his wife Leah on the 180-metre (590-foot) cruise ship carrying them on a five-month voyage around the globe.
"He`s serious about quieting down," Tutu`s spokesman Dan Vaughan said. "He will now be refusing most of the interview requests he receives."
Tutu is currently lecturing on board the ship packed with 600 university students. Friends and family will join him later in the day in the harbour below Cape Town`s landmark Table Mountain for a private birthday party.
Tutu served as archbishop for the Anglican Church in Cape Town, where he still lives when he`s not travelling the world to speak out against injustice and encourage an end to conflicts.
His retirement has been greeted with doubt in South Africa that Tutu will actually step away from public life, with no coverage of his retirement in national media.
"He is going to be missed from public life most definitely. At the same time, one does understand there is a need for him to find some rest and respite after a life-long dedication and commitment to... change in South Africa," political analyst Chris Maroleng said.
"Given his zeal and his determination, I wonder whether he`ll really be able to fully retire as he has indicated."
Tutu says he will continue his work with The Elders, a group of leading statesmen that includes South Africa`s first black president Nelson Mandela, and with a group of fellow Nobel laureates that encourages peaceful ends to conflicts.
He is also still working to develop the Desmond Tutu Peace Centre in Cape Town, where the organisation is building a new complex to house his peace projects.
Tutu won the Nobel Peace Prize in 1984 for his non-violent struggle against apartheid, establishing himself as the voice of the nation`s conscience.
In the years since, he proved indefatigable in leading the Truth and Reconciliation Commission to uncover the horrors of apartheid-era abuses.
Tutu never shied away from shining a spotlight on modern South Africa`s failings, while travelling the globe to promote efforts at peace from the Middle East to the Solomon Islands.