The hosts faced elimination if they had lost but put any nerves to bed in Lyon with 31 unanswered points in the first half, going on to score eight tries for a bonus-point victory.
France advance to the quarter-finals unbeaten and ahead of New Zealand in the group stage rankings.
They will face the runners-up from Pool B – South Africa, Ireland or Scotland – on 15 October.
“Four games, four wins,” said France captain Charles Ollivon. “This was an elimination match for us, we had no right to make mistakes.
“We wanted to play with intensity and we did, and we kept it up for 80 minutes. It’s very positive and sets us up for the next stage. We really want to be there.”
The tone was set inside two minutes when France proved too strong and quick for Italy to work the ball through the hands out to the left wing where Damian Penaud scored his first of two tries. Full back Thomas Ramos was also in unstoppable form with the boot, converting that try before slotting a penalty from halfway.
Louis Bielle-Biarrey again got the nod over Gabin Villiere on the left wing and showed why by collecting a perfect chip from Penaud before jinking around three men to touch down on 13 minutes. Ramos scored the third try by finishing an excellent cross-field move, and the bonus point was secured before half-time when Penaud scored his second, set up by a brilliant kick to the right wing under pressure by Matthieu Jalibert.
Jalibert continued the scoring after half-time, selling the Italian defence with a dummied pass before leaving white shirts trailing on the floor as he touched over, while try number six came from hooker Peato Mauvaka following a line-out.
Replacement back Yoram Moefana brought up the half-century and scored the final two tries, both after superb moves from France that crossed the width of the pitch, while Manuel Zuliani crossed for Italy whose sole comfort was avoiding a shutout.
