Galthié was last month anointed as the successor to head coach Jacques Brunel after the tournament in Japan.
On Tuesday, Brunel said Galthié would concentrate on raising the spirits of the squad before the event starts on 20 September.
"He will be there to bring his vision," Brunel said in a statement posted on the website of the French Rugby Federation. "He already has an idea of what he can bring to us after our discussions and videos that we have watched."
Galthié played for France 64 times between 1991 and 2003. He skippered the side on more than 20 occasions and then went on to coach the Top 14 sides Stade Français, Montpellier and Toulon.
His mission to inject steel and mettle will be onerous. France finished the European Six Nations tournament in fourth place after defeats to Wales, Ireland and England who thrashed them 44-8. It was their heaviest defeat since 1911.
France will have a chance to avenge that humiliation at the World Cup. They have been drawn with England in Pool C along with Argentina, the United States and Tonga.
The World Cup will be Brunel's chance to resuscitate his reputation. Since taking over from Guy Novès in 2017, he has steered the side to just five wins in 16 Tests.