The Dutchman overcame a two-tenth deficit to Alonso in the final sector to make a last-gasp swoop for the fastest time, his resulting 1m11.365s cementing his first pole position in qualifying at the Monte Carlo circuit.
Verstappen had set a banker with a 1m12.102s at the start of the session, but the lap was immediately outclassed by Alonso, who grabbed a 1m11.706s to raise the bar considerably - and felt that he'd "pushed like an animal" to draw first blood.
The Ferraris of Charles Leclerc and Carlos Sainz were unable to beat Alonso's time, but moved ahead of Verstappen in the order as the Red Bull driver was forced to abandon his initial riposte.
Verstappen had another crack on his initial set of tyres and fell slightly short of Alonso in the opening sectors, but nailed the Rascasse and Antony Noghes corners to move to the top with a 1m11.654s.
Esteban Ocon made a surprise charge to the top with a 1m11.553s as the second round of runs began, until Leclerc put his Ferrari above him with a 1m11.471s.
Alonso then charged to provisional pole with a 1m11.449s, sending his Aston Martin mechanics into raptures, but all eyes were on Verstappen as he was set to close out the session.
Verstappen was over a tenth shy in the opening sector and his arrears grew to over two tenths, but he found three tenths over Alonso to dampen Aston Martin's spirits.
Leclerc's lap was good enough to start on the second row, alongside Ocon after the Alpine driver's surprisingly strong effort was enough for fourth. But Leclerc was later penalised three places for impeding Lando Norris, and will start from sixth.
Sainz joined Lewis Hamilton on the third row, as the Mercedes driver scraped through into Q3, as Gasly and Russell filled out the fourth row. Yuki Tsunoda and Lando Norris completed the top 10, the latter able to return to the circuit after tagging the wall at Tabac in Q2.
The McLaren driver damaged the right-hand side of his car, forcing him to abandon the lap that he was on. Nonetheless, his earlier lap was enough to keep him on the right side of the elimination zone.
Norris was judged to have been impeded by Leclerc, which hindered his progress beyond 10th.
Hamilton was also on the brink of elimination having been stranded in the drop zone with time for one more lap, and despite reporting that his tyres weren't ready, the Briton's improvisation was enough to book him a spot into the top 10 at the expense of Oscar Piastri.
Nyck de Vries bagged 12th on the grid ahead of Alex Albon, while Lance Stroll was hamstrung by confusion over his attendance at the weighbridge. The Canadian missed his call to get the car weighed, requiring the Aston Martin mechanics to roll his car back for the FIA to take his corner weights.
Valtteri Bottas will start the race 15th, having been in the top 10 after the initial foray of Q2 runs.
Sergio Perez was the biggest scalp of Q1 after his clash with the wall at Sainte Devote, which brought out the red flag with 11 minutes left on the clock.
The Mexican carried too much speed into the opening corner and, as a result, the rear end of his Red Bull RB19 stepped out. The momentum pushed him towards the exit wall, hitting the Tecpro barrier with his rear-left wheel and causing heavy damage to his rear suspension.
Amid rapid track evolution when the session resumed, Carlos Sainz and Lewis Hamilton were significantly at risk and languished in the drop zone as the Q1 session trickled towards its closing stages.
Sainz had aborted laps, while Hamilton suffered a slip on his penultimate flying lap at the Nouvelle Chicane and rapidly had to regroup for one final push.
Under the pressure, both drivers delivered and managed to progress out of the bottom five, at the expense of the Haas duo as Kevin Magnussen and Nico Hulkenberg were dumped out at the opening stage.
Logan Sargeant leapfrogged the pair of Haas cars while Perez starts last following his crash, alongside Zhou Guanyu.
Revised grid for 2023 Monaco GP
| Cla | Nº | Driver | Car / Engine | Time | Delay [s] |
Delay [%] |
| 1 | 1 | Max Verstappen | Red Bull/Honda RBPT | 1'11.365 | - | - |
| 2 | 14 | Fernando Alonso | Aston Martin/Mercedes | 1'11.449 | 0.084 | 0.118 |
| 3 | 31 | Esteban Ocon | Alpine/Renault | 1'11.553 | 0.188 | 0.263 |
| 4 | 55 | Carlos Sainz Jr. | Ferrari | 1'11.630 | 0.265 | 0.371 |
| 5 | 44 | Lewis Hamilton | Mercedes | 1'11.725 | 0.360 | 0.504 |
| 6 | 16 | Charles Leclerc | Ferrari | 1'11.471 | 0.106 | 0.149 |
| 3-place penalty for impeding Lando Norris |
||||||
| 7 | 10 | Pierre Gasly | Alpine/Renault | 1'11.933 | 0.568 | 0.796 |
| 8 | 63 | George Russell | Mercedes | 1'11.964 | 0.599 | 0.839 |
| 9 | 22 | Yuki Tsunoda | AlphaTauri/Honda RBPT | 1'12.082 | 0.717 | 1.005 |
| 10 | 4 | Lando Norris | McLaren/Mercedes | 1'12.254 | 0.889 | 1.246 |
| 11 | 81 | Oscar Piastri | McLaren/Mercedes | 1'12.395 | 1.030 | 1.443 |
| 12 | 21 | Nyck de Vries | AlphaTauri/Honda RBPT | 1'12.428 | 1.063 | 1.490 |
| 13 | 23 | Alexander Albon | Williams/Mercedes | 1'12.527 | 1.162 | 1.628 |
| 14 | 18 | Lance Stroll | Aston Martin/Mercedes | 1'12.623 | 1.258 | 1.763 |
| 15 | 77 | Valtteri Bottas | Alfa Romeo/Ferrari | 1'12.625 | 1.260 | 1.766 |
| 16 | 2 | Logan Sargeant | Williams/Mercedes | 1'13.113 | 1.748 | 2.449 |
| 17 | 20 | Kevin Magnussen | Haas/Ferrari | 1'13.270 | 1.905 | 2.669 |
| 18 | 27 | Nico Hülkenberg | Haas/Ferrari | 1'13.279 | 1.914 | 2.682 |
| 19 | 24 | Zhou Guanyu | Alfa Romeo/Ferrari | 1'13.523 | 2.158 | 3.024 |
| 20 | 11 | Sergio Pérez | Red Bull/Honda RBPT | 1'13.850 | 2.485 | 3.482 |
