The International Criminal Court (ICC) has overturned the conviction for war crimes and crimes against humanity of former Democratic Republic of Congo Vice-President Jean-Pierre Bemba, according to the BBC.
Bemba was found guilty in 2016 of crimes committed in the neighbouring Central African Republic (CAR) in 2002-2003.
He was accused of failing to stop his rebels from killing and raping people.
But a judge has now said he cannot be held responsible for their actions.
Christine Van den Wijngaert also said the judges in the 2016 case had failed to take into account his attempts to stop the crimes once he was made aware they were taking place.
The decision to overturn the 18-year sentence was greeted by cheers from his supporters in the gallery.
But human rights group Amnesty International said it was a "huge blow" for the victims of a "horrifying campaign of rape and sexual violence", as it called on the authorities to redouble their efforts to prosecute those who had carried it out.
More than 5,000 survivors took part in the proceedings against Bemba, said Amnesty's head of international justice, Solomon Sacco.
"For these brave individuals, as well as thousands of other victims in CAR, the pursuit of truth, justice and reparations will continue," he added.