Leclerc had previously set an identical Q3 time with rival Max Verstappen as both drivers notched a 1m40.445s, but it was the Red Bull racer who lapped first to provisionally hold the top spot.
But Leclerc fought back in the dying moments with a personal best first and final sector in addition to running faster than anyone through the middle part of the lap to bank a 1m40.203s to pip Verstappen by 0.188s.
This was helped by both Verstappen and his team-mate Sergio Perez dropping time in the second sector to fall short of their personal best time.
Leclerc said the pre-weekend team target had been to beat Aston Martin and Mercedes, leaving him shocked to have scored his first pole since Singapore in 2022 and to have ended the Red Bull qualifying streak in the early part of this season.
“I'm surprised,” he said. “We came into the weekend thinking that it will be a great weekend if we are in front of Aston and Mercedes in qualifying and, at the end, we are on pole, so it's a really good surprise.”
However, Leclerc did lower expectations for the full grand prix on Sunday as he acknowledged that the race pace of the RB19 was still likely to trump that of his SF-23 machine.
He continued: “We must not forget that our race car is maybe still behind the Red Bulls, so it's going to be difficult to keep the lead but that's the target and really, really happy with the lap.
“It's a very challenging weekend overall for us drivers because very little time to practice [with the changes to the sprint race event timetable].
“We only had one practice and then you need to be straight on it, but the feeling was good since the start so really, really happy.”
With Ferrari team-mate Carlos Sainz clocking fourth behind Perez, Leclerc added: “It's going be challenging because we haven't run the medium [tyre compound] yet.
“So tomorrow in qualifying [for the sprint race] will be the first time and we need to be on it because we only have one set. So, no room for mistake.
“But again, the pace seems strong. So, hopefully we can learn in Q1 and Q2 and then push in Q3 and we know the car is good.”
