President Francois Hollande will take part in a march in memory of the victims in Tunis on Sunday
A fourth French national has died of her wounds following the March 18 attack on Tunisia's national museum, the French president's office said in a statement on Saturday.
The statement named the deceased as Mrs Dupeu but gave no further details.
Japanese, Italian, Spanish and British visitors, as well as Tunisians, were among the 22 victims of the attack, which took place in the heavily guarded parliament compound of a country largely spared the violent aftermath of the Arab Spring.
French President Francois Hollande will take part in a march in memory of the victims in Tunis on Sunday. The militant group ISIL has claimed responsibility for the attack.