Max Verstappen set a searing pace in final practice that will have opened the eyes of Ferrari after the Scuderia had dominated the Friday sessions.
After Charles Leclerc was quickest in FP1 and team-mate Carlos Sainz spearheaded a one-two in the later hour-long run, reigning F1 champion Verstappen had expressed a degree of concern following a day of experimenting from Red Bull.
But the Dutch driver, who leads the standings by 38 points from Leclerc, again looks the man to beat in qualifying after posting a time of one minute 32.272secs towards the end of the session once the teams began their soft-tyre runs.
Verstappen had also been quickest on the medium compound earlier in the session at the Paul Ricard Circuit where Leclerc appears to be his only challenger.
That is due to the fact Ferrari confirmed an as-expected complete power unit change for Sainz who will start at the back of the grid alongside Kevin Magnussen whose Haas team has also been forced into a PU change.
Sainz was second fastest but a staggering 0.354s down, with Leclerc a further third of a second off the pace.
For the session, Lewis Hamilton ran a higher downforce developmental rear wing on his W13, albeit one that significantly hampered his straight-line speed early on.
At one stage, Hamilton was 1.784s adrift of Verstappen to which he aired over the radio with clear surprise "Jeez! 1.7 seconds!", underlining the component was not working as had perhaps been expected.
After set-up changes, Hamilton managed to close the gap on Verstappen to just under a second, with the seven-time champion followed by Sergio Perez and Mercedes team-mate George Russell, the latter 1.104s down.
Fernando Alonso offered a degree of home comfort to French fans as he managed to haul his Alpine up to seventh on the teamsheet, 1.233s down, and six-tenths of a second faster than team-mate Esteban Ocon who was left languishing in 17th.
Williams' Alex Albon, Lando Norris in his McLaren and Yuki Tsunoda for AlphaTauri rounded out the top 10, with the latter 1.479s back.
Remarkably, with the top four covered by a second, from Hamilton in fourth to Mick Schumacher in 19th for Haas, those 16 places were covered by another second.
Aston Martin's Sebastian Vettel endured a troubled session, completing just 11 laps to leave the four-time champion propping up the timesheet, 2.264s back.
French Grand Prix final practice results
1. Max Verstappen [Red Bull[ 1:32.272s
2. Carlos Sainz [Ferrari] +0.354s
3. Charles Leclerc [Ferrari] +0.637s
4. Lewis Hamilton [Mercedes] +0.983s
5. Sergio Perez [Red Bull] +1.021s
6. George Russell [Mercedes] +1.104s
7. Fernando Alonso [Alpine] +1.233s
8. Alex Albon [Williams] +1.286s
9. Lando Norris [McLaren] +1.397s
10. Yuki Tsunoda [AlphaTauri] +1.479s
11. Daniel Ricciardo [McLaren] +1.516s
12. Nicholas Latifi [Williams] +1.569s
13. Pierre Gasly [AlphaTauri] +1.597s
14. Valtteri Bottas [Alfa Romeo] +1.600s
15 Zhou Guanyu [Alfa Romeo] +1.639s
16. Kevin Magnussen [Haas] +1.759s
17. Esteban Ocon [Alpine] +1.850s
18. Lance Stroll [Aston Martin] +1.905s
19. Mick Schumacher [Haas] +1.950s
20. Sebastian Vettel [Aston Martin] +2.264s