French government spokeswoman Cecile Pozzo di Borgo confirmed on Sunday that Florence Aubenas was free and had already left Baghdad airport for home.
Her guide and translator, Husain Hanun al-Saadi, has also been released.
Aubenas worked for the French newspaper Liberation. She and al-Saadi were taken hostage after leaving their hotel in Baghdad on 5 January.
Their captors released video footage of Aubenas on 1 March. Looking distraught and fragile, she made a desperate appeal for help.
France's opposition to the US-led war in Iraq may have helped it secure the release of the pair, as it did in the case of two French journalists freed in Iraq in December after four months of being held hostage.
Meanwhile, two Romanian hostages freed last month have said they were held with Aubenas.
"We are incredibly happy that she has been freed, because we were held in the same place for almost a month and a half, from the first of April," journalist Marie-Jeanne Ion told Romania's Realitatea TV.
The hostages celebrate with
President Traian Basescu (C)
"Florence was remarkable throughout. She constantly encouraged us. She is amazingly strong."
Sorin Miscoci - the cameraman held with Ion and a third Romanian journalist - said he was extremely happy to learn that Aubenas had been freed after her five-month-long ordeal.
"We have kept quiet about the details of our captivity in Iraq precisely because we hoped Florence would be released," Sorin added.
Since their release on 22 May, the Romanian journalists had said they needed to be vague about their time in captivity so as not to endanger others still being held in Iraq.
Romanian President Traian Basescu also said last week he was not authorised to reveal how the authorities secured their release as "the Romanian government is not the only one involved in this operation".
About 150 foreigners have been seized in Iraq over the past two years. Many more Iraqis have been abducted.