A Rwandan court in the capital, Kigali, has acquitted government critic Diane Rwigara and her mother of charges of inciting insurrection and forgery.
Ms Rwigara was imprisoned for over a year, after being barred from running in presidential elections against the long-standing incumbent Paul Kagame.
The 37-year-old opposition leader faced up to 22 years in prison for charges she said were politically motivated.
A three-judge panel told a packed room all the charges were "baseless".
Amnesty International welcomed the result, but said the mother and daughter "should never have faced charges for expressing their views".
Since her arrest, Ms Rwigara's family have been subject to interrogations and their family assets forcibly auctioned.
"I am very happy with the verdict," said Ms Rwigara, who has been out on bail since October. "I am continuing with my political journey... because there's still a lot that needs to be done in our country."
During the hearings, the businesswoman asserted that Rwanda's economy was mainly controlled by the governing party's elite.
"Everything I talked about in the past has not been resolved. There are still many political prisoners in the country," she told journalists after the high court ruling.
Ms Rwigara has repeatedly accused President Kagame of stifling dissent and criticised his party's unyielding grip on power since it assumed control after the country's civil war.
Dissent still not tolerated
Anne Soy, BBC Africa correspondent
The acquittal of Diane Rwigara and her mother Adeline could be seen a significant step in Rwanda's democracy.
But it is also hard to ignore the fact that there was international pressure, including from the US Congress, to drop charges against her - not that Rwandan authorities are in the habit of listening to external voices.
Critics still see Ms Rwigara's arrest and detention, and the auctioning of her assets, as a continuation of a trend of intimidation against anyone who opposes the government. And there's a long list of dissidents who have been punished severely.
Opposition leader Victoire Ingabire was released from prison this year having served time for "conspiracy against the country through terrorism and war" and "genocide denial." She - just like Ms Rwigara - had intended to run for president against Paul Kagame, back in 2010.
Another opposition leader, Boniface Twagirimana, went missing from prison in October. His whereabouts remain unknown.
Ms Ingabire was released in September under the president's prerogative of mercy, a move that could be interpreted as painting Mr Kagame as the benevolent leader.
But the underlying message remains that dissent will not be tolerated.
In Thursday's ruling, the high court judges said the prosecution failed to prove that Ms Rwigara had personally forged supporters' signatures and ruled that her criticism of the government during press conferences was protected by freedom of speech in both the constitution and international law.
They also ruled freedom of speech protected the Whatsapp voice notes Adeline Rwigara privately sent to relatives accusing the state of ruling through fear.