Sergio Perez posted the first representative lap time with a 1m15.641s to go top, managing to avoid a stopped Esteban Ocon in the tunnel as the Alpine driver reported a loss of power.
The Frenchman returned his car to the pits after a swift reset at the steering wheel, but this forced him to spend the next 20 minutes in the garage.
Pierre Gasly found a glimmer of hope for Alpine by going quicker than Perez, but the Mexican responded with a 1m14.990s to go back to the top - holding firm from the Ferrari duo's first fast laps on softs.
Lando Norris then shaded Perez by 0.005s, until Lance Stroll placed a 1m14.763s on the table to briefly sit at the top of the session. Perez quickly dispatched the Canadian with a 1m14.377s, as the circuit began to progress in terms of available grip.
The 1m14s barrier was then broken by Max Verstappen, who went half a second clear of Perez but was surpassed by fellow two-time champion Fernando Alonso and his 1m13.697s lap.
Perez returned to head the order as the opening half-hour of the session drew to a close, finding a tenth over Alonso, but Verstappen found 0.004s over his team-mate to restore a Red Bull 1-2.
The two swapped places once more, Perez finding a 1m13.289s as Carlos Sainz dropped into second just 0.09s away, until a 1m12.898s for Verstappen raised the bar once more.
While Perez hit back with a 1m12.849s, Verstappen put in a 1m12.776s to continue Red Bull's duopoly over the Saturday practice session. This was challenged later by Stroll, but the Canadian was just under a tenth shy of challenging Perez and could not split the RB19s out front.
As the session moved into the final 10 minutes, Kevin Magnussen initially had an off at Sainte Devote and went down the escape road. Moments after his recovery, he came to a halt at Portier and produced a virtual safety car - stopping a potential Alonso tilt for the fastest lap as he had set the best first sector.
Moments after the session resumed at full speed, Hamilton put his Mercedes into the barrier on the exit of Mirabeau. The Briton had just flashed up with the fastest opening sector, but overshot his braking area and slid into the Armco front-on.
As a result of the clearance of Hamilton's stranded Mercedes, the session was not resumed to ensure Verstappen's time could not be challenged any further.
Perez and Stroll were the only other drivers in the 1m12s, as Sainz was the fastest of those in the 1m13s bracket to finish the session in fourth.
Norris claimed the fifth best time over Gasly and Charles Leclerc, who reported struggles with the Swimming Pool section and stated that he needed to lift to exert any control over the Ferrari's trajectory.
Hamilton's crash denied him the chance to improve on eighth, as Ocon returned to the track after his earlier issues to grab the ninth-best time. Valtteri Bottas completed the top 10, fractions clear of George Russell.
| Cla | Driver | Chassis | Engine | Laps | Time | Gap | Interval | |
|---|---|---|---|---|---|---|---|---|
| 1 |  Max Verstappen |
 |
Red Bull | Red Bull | 19 | 1'12.776 | ||
| 2 |  Sergio Perez |
 |
Red Bull | Red Bull | 24 | 1'12.849 | 0.073 | 0.073 |
| 3 |  Lance Stroll |
 |
Aston Martin | Mercedes | 20 | 1'12.942 | 0.166 | 0.093 |
| 4 |  Carlos Sainz |
 |
Ferrari | Ferrari | 20 | 1'13.261 | 0.485 | 0.319 |
| 5 |  Lando Norris |
 |
McLaren | Mercedes | 21 | 1'13.396 | 0.620 | 0.135 |
| 6 |  Pierre Gasly |
 |
Alpine | Renault | 24 | 1'13.453 | 0.677 | 0.057 |
| 7 |  Charles Leclerc |
 |
Ferrari | Ferrari | 19 | 1'13.475 | 0.699 | 0.022 |
| 8 | Lewis Hamilton |
 |
Mercedes | Mercedes | 17 | 1'13.486 | 0.710 | 0.011 |
| 9 | Esteban Ocon |
 |
Alpine | Renault | 18 | 1'13.496 | 0.720 | 0.010 |
| 10 |  Valtteri Bottas |
 |
Alfa Romeo | Ferrari | 20 | 1'13.521 | 0.745 | 0.025 |
| 11 | George Russell |
 |
Mercedes | Mercedes | 18 | 1'13.590 | 0.814 | 0.069 |
| 12 |  Kevin Magnussen |
 |
Haas | Ferrari | 13 | 1'13.624 | 0.848 | 0.034 |
| 13 |  Nico Hulkenberg |
 |
Haas | Ferrari | 16 | 1'13.650 | 0.874 | 0.026 |
| 14 | Fernando Alonso |
 |
Aston Martin | Mercedes | 18 | 1'13.697 | 0.921 | 0.047 |
| 15 |  Yuki Tsunoda |
 |
AlphaTauri | Red Bull | 21 | 1'13.738 | 0.962 | 0.041 |
| 16 |  Zhou Guanyu |
 |
Alfa Romeo | Ferrari | 20 | 1'13.772 | 0.996 | 0.034 |
| 17 |  Logan Sargeant |
 |
Williams | Mercedes | 19 | 1'13.851 | 1.075 | 0.079 |
| 18 |  Alex Albon |
 |
Williams | Mercedes | 23 | 1'13.930 | 1.154 | 0.079 |
| 19 |  Oscar Piastri |
 |
McLaren | Mercedes | 18 | 1'13.998 | 1.222 | 0.068 |
| 20 | Nyck de Vries |
 |
AlphaTauri | Red Bull | 24 | 1'14.187 | 1.411 | 0.189 |
| View full results | ||||||||
