French Armed Forces Minister Florence Parly thanked the militaries of Benin and Burkina Faso for their help in the operation and said the US had provided "precious" support.
Who are the hostages?
Frenchmen Patrick Picque and Laurent Lassimouillas, both music teachers, disappeared in the remote Pendjari National Park in Benin where they had been on safari. Their local guide was found dead.
The park is on the border with Burkina Faso where Islamist militants have been increasingly active in recent months.
No further details of the other two hostages liberated were given.
South Korean media quoted a government official as saying the authorities had no report of a missing citizen and they were trying to establish the rescued woman's citizenship.
What reaction has there been?
A statement from the French said President Emmanuel Macron "bows with emotion and solemnity before the sacrifice of our two soldiers who gave their lives to save those of our citizens".
Ms Parly said "terrorists who attack France and French citizens should know that we will spare no effort to track them down and fight them".
France has 4,500 troops based in the Sahel region on the southern edge of the Sahara Desert as part of its Operation Barkhane - an ongoing coalition effort in Africa's Sahel region to fight jihadist insurgents.