Ferrari's Leclerc secures pole at the Azerbaijan Grand Prix for third year in a row
Leclerc's pole, acquired in a session twice red-flagged due to crashes, was Ferrari's first of the Formula One season and ended Red Bull's run of three in succession.
Red Bull's championship leader Max Verstappen qualified second-fastest with his teammate Sergio Perez third.
Drivers will have another qualifying on Saturday for a standalone 100 km sprint race that no longer determines Sunday's grid after a new format was agreed upon unanimously by teams this week.
"It feels good...It's good to be back on top," said Leclerc after whooping in delight over the team radio.
There was nothing to separate him and Verstappen after the initial flying laps, with both clocking 1:40.445 seconds but the Red Bull driver on provisional pole due to setting his time first.
Leclerc made sure he got his second lap in first, lowering the benchmark to 1:40.203 - with Verstappen unable to beat it and ending up 0.188 slower.
"We came into the weekend thinking that it would be a great weekend if we were in front of Aston Martin and Mercedes in qualifying," said the Ferrari driver, whose team-mate Carlos Sainz qualified fourth.
"And at the end, we are on pole, so it's a good surprise," added the Monegasque, who has yet to win at a circuit that has yet to see a repeat winner or indeed anyone not driving a Red Bull or a Mercedes.
"We must not forget that our car is probably behind the Red Bull, so it's going to be difficult to keep the lead. But that's the target," added Leclerc.
Verstappen, winner in Baku last year, was sanguine about the session.
"We are P2, we know we have a very good race car so all in all it's not bad. You want to start ahead but we'll have to pass one car," he said.
Seven-times world champion Lewis Hamilton put his Mercedes fifth on the grid, with Aston Martin's Fernando Alonso alongside.
Lando Norris will line up seventh in an upgraded McLaren with AlphaTauri's Yuki Tsunoda eighth and Lance Stroll's Aston Martin and Oscar Piastri's McLaren on the row behind.
Hamilton only just scraped through to the final top-10 shootout, beating team-mate George Russell by a mere 0.004.
"Ah, sugar," Russell exclaimed in frustration when told he had failed to make the cut.
The first phase was halted with 10 minutes to go after Nyck de Vries took too much speed into turn three, locked up and speared his AlphaTauri nose-first into the Tecpro barrier.
The session resumed after a 16-minute delay to extract the wrecked car.
Alpine's Pierre Gasly started the opening session after his mechanics hurriedly replaced the gearbox and power unit following a fire in practice but any joy was short-lived.
Gasly had red flags waving for the second time, triggering another delay, when he also hit the wall at turn three with seven and a half minutes to go.
"I'm sorry, I locked the fronts," said the Frenchman, who qualified 19th, over the radio.
Haas drivers Nico Hulkenberg and Kevin Magnussen qualified 17th and 18th respectively with Alfa Romeo's Guanyu Zhou also failing to make it through the first phase when Leclerc was also quickest.