Ferrari's Kimi Raikkonen took pole position for the showcase Monaco Grand Prix on Saturday with world championship leading German team mate Sebastian Vettel alongside him on the front row.
Britain's triple champion Lewis Hamilton, six points behind Vettel in the Formula One standings after five races, suffered a major blow as he is set to start 13th.
Hamilton has struggled for pace all weekend in Monte Carlo, but his failure to progress to the top-10 shootout will come as an almighty shock to Hamilton and his Mercedes team.
Raikkonen secured the number one spot - his first in nearly a decade - after seeing off the challenge from Hamilton's championship rival Vettel by just 0.043 seconds as Ferrari sealed a front-row lockout. Hamilton's Mercedes team-mate Valtteri Bottas lines up in third.
An impressive Jenson Button posted the ninth best time on his return to Formula One action, but he will start from the very back after he was dealt a 15-place grid penalty following a series of changes to his Honda engine.
Hamilton, 32, arrived in Monaco bidding to join childhood hero Ayrton Senna on 65 poles - 30 years after the Brazilian secured his first of a record six wins here - but after going fastest in opening practice on Friday, Hamilton has slid back down the order, and his erratic display in qualifying was that of a man struggling for confidence.
Hamilton endured two hairy moments where he almost collided with the barriers, first at Massenet and then at Mirabeau, before he claimed something was not right with his Mercedes car.
And the Briton's last-gasp attempt to make it into Q3 was destroyed when Stoffel Vandoorne lost control of his McLaren and crashed into the wall at the swimming pool chicane.
Hamilton had to slow right down, and with the allocated time over, the Briton was left with no option but to pull into the pits. He qualified 14th, 1.8 seconds off the pace, but will be bumped up one spot following Button's penalty.
Hamilton, shaking his head as he arrived in the Mercedes garage, will take some joy from the fact that it is Raikkonen, who starts on pole for the first time since the 2008 French Grand Prix, and not Vettel. But the Englishman will still have it all to do in tomorrow's race with overtaking almost impossible at this most twisty and narrow of tracks.
Hamilton's countryman Button is back in a grand prix car for the first time since he walked away from the sport last November in Abu Dhabi.
His McLaren has been competitive here and his ninth place in qualifying showed he still has the speed to compete, but his penalty means he will be at the very back on Sunday and - like Hamilton - faces an almost impossible task of salvaging a strong result.
British driver Jolyon Palmer is looking for a spark to re-ignite his poor campaign, but the Renault driver has been slow once more here.
The 26-year-old from Horsham has occupied lower echelons of the order over the course of the weekend, and he was only 17th of the 20 runners in qualifying.
Indeed Palmer was nearly one second slower than his Renault team-mate Nico Hulkenberg, who comfortably progressed to Q2 before posting the 12th best time.
Elsewhere, Max Verstappen and Daniel Ricciardo were fourth and fifth for Red Bull with Toro Rosso's Carlos Sainz an impressive sixth.