The Mercedes driver unleashed a stunning 1m12.720s late in the session, becoming the first driver to break into the 1m12s and finishing 0.327s clear of Ferrari’s Charles Leclerc.
Lewis Hamilton was third for Ferrari, just 0.004s behind teammate Leclerc, while George Russell was fourth in the second Mercedes.
Max Verstappen ended the session fifth for Red Bull, with Oscar Piastri sixth and the only other driver within a second of Antonelli’s benchmark.
Antonelli’s final effort was particularly impressive given he left time on the table in the final sector, having already set overall fastest times in the opening two sectors.
Ferrari had looked set to continue the dominance it displayed throughout Friday after Leclerc and Hamilton traded fastest times during the opening stages of the session.
Hamilton was first on track under bright Monaco sunshine and initially set the pace before Leclerc edged ahead by just 0.062s as the field worked through its early soft-tyre runs.
Russell then briefly moved Mercedes to the top with a 1m13.902s before Leclerc responded with a 1m13.748s, while Antonelli steadily built into the session after a relatively quiet start.
McLaren’s early running was led by Lando Norris, who was the first driver into the 1m14s before returning to the pits for adjustments. Piastri joined the action slightly later and immediately slotted himself into contention near the front.
As track conditions improved, Antonelli began to stamp his authority on the session.
The Italian first lowered the benchmark to a 1m13.374s before finding another two tenths to record a 1m13.137s, remaining comfortably ahead despite continued pressure from Leclerc.
Verstappen, meanwhile, struggled to match the pace of Mercedes and Ferrari and spent much of the session outside the top five before eventually climbing to fifth.
Piastri climbed to sixth with a 1m13.698s, although neither McLaren driver featured prominently in the final battle for top spot.
The decisive phase arrived in the final 10 minutes as Mercedes and Ferrari bolted on fresh soft tyres for qualifying simulations.
Antonelli delivered the standout lap of the weekend with a stunning first two sectors before stopping the clocks at 1m12.720s.
Leclerc looked capable of mounting a challenge after improving through the opening sectors of his own lap, but traffic at Rascasse forced him to abandon the attempt, leaving him second ahead of Hamilton.
Russell struggled to find a clean lap during the closing stages and ultimately finished more than seven tenths behind his teammate in fourth.
The session was then interrupted by a red flag with eight minutes remaining when Oliver Bearman crashed at Massenet.
Ollie Bearman crashes out of FP3 😱
Here is how the moment happened at Massenet 👇#F1 #MonacoGP pic.twitter.com/S7ME5vNxft
— Formula 1 (@F1) June 6, 2026
The Haas driver lost the rear of the car on entry to the fast left-hander and struck the barriers, damaging the rear wing but reporting over team radio that he was unhurt.
Barrier repairs delayed the restart, leaving only a handful of minutes remaining when the green flag finally returned.
A frantic final dash followed, although few drivers were able to improve significantly as teams scrambled to complete their final preparations before qualifying.
Earlier in the session, several incidents punctuated the running as drivers continued to flirt with Monaco’s unforgiving barriers.
Franco Colapinto brought out a brief yellow flag after a half-spin at the Fairmont Hairpin, appearing to clip the barrier with the rear of his Alpine before returning to the pits.
Liam Lawson also survived a major scare through the Swimming Pool section after his Racing Bulls machine bounced aggressively over a kerb and snapped sideways at high speed.
Elsewhere, Cadillac endured another frustrating session after both Sergio Perez and Valtteri Bottas reported brake issues. Perez complained of a front brake fire early in the session, while Bottas reported smoke from his right-front corner.
Behind the leading teams, Audi continued its impressive Monaco form with Gabriel Bortoleto seventh and Nico Hulkenberg 10th, while Isack Hadjar and Norris split the pair in eighth and ninth.
Esteban Ocon was 11th ahead of Carlos Sainz and Pierre Gasly, while Bearman finished 14th despite his crash, just ahead of Lawson in 15th.
Alex Albon was 16th for Williams ahead of Racing Bulls rookie Arvid Lindblad, while Perez managed 18th for Cadillac ahead of Colapinto. Bottas was 20th and finished ahead of the Aston Martin pair of Fernando Alonso and Lance Stroll, who once again brought up the rear of the field.
Qualifying for the Monaco Grand Prix starts at 4pm local time (midnight AEST).
Results: Formula 1 Monaco Grand Prix, Free Practice 3
| Pos. | No. | Driver | Team | Time / Gap | Laps |
| 1 | 12 | Kimi Antonelli | Mercedes | 1:12.720 | 22 |
| 2 | 16 | Charles Leclerc | Ferrari | +0.327s | 32 |
| 3 | 44 | Lewis Hamilton | Ferrari | +0.331s | 30 |
| 4 | 63 | George Russell | Mercedes | +0.763s | 23 |
| 5 | 3 | Max Verstappen | Red Bull Racing | +0.942s | 23 |
| 6 | 81 | Oscar Piastri | McLaren | +0.978s | 20 |
| 7 | 5 | Gabriel Bortoleto | Audi | +1.100s | 27 |
| 8 | 6 | Isack Hadjar | Red Bull Racing | +1.157s | 25 |
| 9 | 1 | Lando Norris | McLaren | +1.286s | 24 |
| 10 | 27 | Nico Hulkenberg | Audi | +1.330s | 22 |
| 11 | 31 | Esteban Ocon | Haas F1 Team | +1.558s | 24 |
| 12 | 55 | Carlos Sainz | Williams | +1.616s | 26 |
| 13 | 10 | Pierre Gasly | Alpine | +1.760s | 22 |
| 14 | 87 | Oliver Bearman | Haas F1 Team | +1.767s | 18 |
| 15 | 30 | Liam Lawson | Racing Bulls | +1.867s | 27 |
| 16 | 23 | Alexander Albon | Williams | +2.081s | 24 |
| 17 | 41 | Arvid Lindblad | Racing Bulls | +2.198s | 24 |
| 18 | 11 | Sergio Perez | Cadillac | +2.225s | 19 |
| 19 | 43 | Franco Colapinto | Alpine | +2.459s | 21 |
| 20 | 77 | Valtteri Bottas | Cadillac | +2.731s | 17 |
| 21 | 14 | Fernando Alonso | Aston Martin | +2.847s | 26 |
| 22 | 18 | Lance Stroll | Aston Martin | +3.201s | 22 |























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