Jacqueline Sauvage's husband was a violent alcoholic who, she said, had raped and beaten her and her daughters for decades.
She also said he had abused their son, who killed himself.
More than 400,000 people signed a petition calling on Mr Hollande to intervene.
The sentence reduction means the 68-year-old will now be able to leave jail in mid-April, her lawyers said.
On 10 September 2010, the day after her son's suicide, Sauvage shot her husband three times in the back with a rifle.
She was found guilty and sentenced to 10 years in prison in October 2014, which was upheld on appeal in December 2015 after the state rejected her plea of self-defence.
The case became a cause celebre in France, with campaigners calling for the definition of self-defence to be expanded to encompass victims of violence.
The move does not quash Sauvage's conviction but waives the remainder of her sentence.
"In the face of an exceptional human situation, the president wanted to make it possible for Sauvage to return to her family as soon as possible," the presidency said in a statement.
The decision came two days after Mr Hollande met Sauvage's three adult daughters.
French President Francois Hollande has waived the remaining prison sentence of a woman who was sentenced to 10 years for murdering her abusive husband.