Guineans are expected to celebrate the landmark with concerts and fireworks.
Sierra Leone was declared free of Ebola in November, but new cases have been discovered in Liberia, which had been declared Ebola-free in September.
The disease killed more than 2,500 people in Guinea, and a further 9,000 in Sierra Leone and Liberia.
Even though there has not been any new cases of Ebola in 42 days, local health workers in Guinea and the World Health Organisation warned that people should still be very careful.
"The coming months will be absolutely critical," said Dr Bruce Aylward from the World Health Organisation's Ebola response team.
"This is the period when the countries need to be sure that they are fully prepared to prevent, detect and respond to any new cases."

The left-wing MP, who has gone from outsider to frontrunner, said Saturday was not the end of inspiration for the campaign, but the "staging post".
It comes as some of his rival candidates appeared to concede victory.
Unite union boss Len McCluskey said the MP had "already won" in his eyes, as he had "lit up" the Labour movement.
"Jeremy, in that calm fashion, seems to have touched a pulse, and that pulse is about people rejecting the constant downbeat austerity message that's been coming out of politics for 35 years," he told the BBC.
Mr Corbyn is up against shadow health secretary Andy Burnham, shadow home secretary Yvette Cooper and shadow health minister Liz Kendall for the top job.
He was a last-minute addition to the ballot after some Labour MPs "lent" him their nomination, saying they wanted to broaden the debate.
But the popularity of Mr Corbyn's campaign has fuelled a bitter row within the party over the its future direction, with warnings from his rival candidates and senior figures, including former prime minister Tony Blair, against a shift to the left.
Attending his 99th rally, held in the Islington North constituency in London which he has represented since 1983, Mr Corbyn said his campaign had been one of "hope" and "optimism" and promised to "change politics".
He told supporters: "This inspiration that's been the last 100 days doesn't end on Saturday. Saturday is simply one staging post in it.
"We change politics in Britain, we challenge the narrative that only the individual matters... and instead we say the common good is the aspiration of all of us."
The MP said he looked forward to Saturday with "interest, if not some anticipation".
Ahead of the event, the bookies' favourite in the contest told Channel 4 News he was not "scared" at the prospect of taking on his party's top job.
He also said he was "extremely confident" of being able to build a shadow cabinet, saying: "I've had many discussions with people already about how we are going to take these things forward."
Mr Corbyn's speech came hours after voting in the Labour leadership closed, bringing three months of campaigning by the candidates to an end.
In an email to supporters, Mr Burnham said he had an "outside but realistic chance" of winning the contest, and that getting this far was "a real achievement".
BBC political editor Laura Kuenssberg said it was seen by some of his supporters as an admission of defeat - but a campaign source said this was "categorically not" the case.
Mr Burnham also said "thousands of ordinary, decent party members are now worried about where we are heading".
In the closing speech of her campaign, Ms Kendall - who has stressed the need for Labour to appeal to a broader section of the electorate - said she may have been "too blunt" at times.
She added: "But my view is that in politics, as in life, you cannot deal with problems by ignoring or avoiding them."
The contest has been plagued by internal rows over Labour's direction and concerns that non-party supporters have tried to influence the outcome through the new system allowing people to sign up as a registered supporter for Â£3, entitling them to vote in the election.
There have also been claims from some people that they did not receive their ballot papers in time to vote, but Labour said ballots had been emailed and posted out correctly to everyone entitled to vote.
The party said everyone who had not voted or said they did not have a ballot had received a final email reminder on Tuesday.
Labour's new deputy leader will also be unveiled at the leadership conference on Saturday, while its candidate for the 2016 London mayoral elections will be announced on Friday.
The World Health Organisation has declared Guinea, in West Africa, free of Ebola, two years after the outbreak of the virus began there.
[NEXT_CONCEPT]
Labour leadership hopeful Jeremy Corbyn has thanked his supporters at a final rally before the result of the three-month contest is announced.