More than a dozen current and former leaders, including South African President Cyril Ramaphosa, are expected to attend. A national sports stadium is expected to be filled with well-wishers.
The funeral follows a row between the Mugabe family and the government over his burial.
Some dignitaries, including Equatorial Guinea President Theodore Obiang Nguema, have already arrived.
Mr Obiang, who came to power in 1979 and has so far outlasted Mr Mugabe’s 30-year rule by a decade, said he was “a leader without comparison on the African continent” and praised his controversial policy of seizing white-owned farms.
Like Mr Obiang, many Zimbabweans are choosing to remember the former leader’s achievements, rather than the political violence and economic chaos that marked the last years of his long presidency, reports BBC Africa correspondent Andrew Harding. “The people of Zimbabwe will forever be grateful that he took land from the whites and gave it to his people,” he said.
His successor as president, Emmerson Mnangagwa, will address mourners at the National Sports Stadium, where thousands will wear the colours of the ruling Zanu-PF party.
But many people in Harare are likely to shun the ceremony as soaring inflation and unemployment grip the country.
When and where will Mugabe be buried?
Zimbabwe’s former President Robert Mugabe will be buried in the National Heroes’ Acre monument in Harare, his family says, following a row with the government over his final resting site.
Family spokesman and nephew Leo Mugabe says this should be in about a month, when the new shrine to Mugabe will be built at the existing Heroes’ Acre.
Earlier plans to have a burial on Sunday appear to have been cancelled.
Mr Mugabe, who was 95, died last week while being treated in Singapore. His body is now lying in state at the Rufaro football stadium in the capital before the funeral on Saturday.
Who was Robert Mugabe?
Mr Mugabe was Zimbabwe’s first leader after the country became independent in 1980. He held on to power for almost four decades before being ousted in the 2017 coup.
During his early years, he was praised for broadening access to health and education for the black majority.
However his later years were marked by violent repression of his political opponents and Zimbabwe’s economic ruin. An increasing number of critics labelled him a dictator.
He seized land from white owners in 2000.
Mr Mugabe famously declared that only God could remove him from office.
In 2017 he was placed under house arrest and, four days later, replaced as the leader of his party Zanu-PF by his former vice president, Emmerson Mnangagwa.
Mr Mugabe initially refused to resign. But, on 21 November, as a motion to impeach him was being debated in the Zimbabwean parliament, the speaker of the House of Assembly announced that he had finally left office.
Mr Mugabe negotiated a deal which protected him and his family from the risk of future prosecution and enabled him to retain his various business interests. He was also granted a house, servants, vehicles and full diplomatic status.